1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
2 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
4 <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
5 <meta http-equiv="Content-Language" content="en" />
6 <meta name="description" content="htmLawed PHP software is a free, open-source, customizable HTML input purifier and filter - htmLawed_README.txt - presented with rTxt2htm, a PHP Labware utility" />
7 <meta name="keywords" content="htmLawed, HTM, HTML, HTML5, HTML 5, XHTML, XHTML5, HTML Tidy, converter, filter, formatter, purifier, sanitizer, XSS, input, PHP, software, code, script, security, cross-site scripting, hack, sanitize, remove, standards, tags, attributes, elements, Aria, Ruby, data attributes, tidy, indent, auto-indent, prettify, pretty print, htmLawed_README.txt, rTxt2htm, PHP Labware" />
8 <style type="text/css" media="all">
9 <!--/*--><![CDATA[/*><!--*/
10 a {text-decoration:none; color: blue;}
\r
11 a:hover {color: red;}
\r
12 a:visited {color: blue;}
\r
13 body {margin: 0; padding: 0;}
\r
14 body, div, html, p {font-family: Georgia, 'Times new roman', Times;}
\r
15 code.code {font-family: 'Bitstream vera sans mono', 'Courier New', 'Courier', monospace;}
\r
16 div.comment {padding: 5px; color: #999999; font-size: 80%;}
\r
17 div.comment a {color: #6699cc;}
\r
18 div#body {width: 70%; margin: 5px; padding: 5px;} /* holds non-toc content */
\r
19 div#toc {position: fixed; top: 5px; left: 73%; z-index: 2; margin-top: 5px; margin-left: 5px; border: 1px solid gray; padding: 5px; background-color: #ededed; width: 23%; overflow: auto; max-height:94%; font-size: 90%;} /* holds content table (toc) */
\r
20 div#top {font-size: 14px; margin: 5px; padding: 5px;} /* holds all content */
\r
21 div.monospace {overflow: auto; font-family: 'Bitstream vera sans mono', 'Courier New', 'Courier', monospace;}
\r
22 div.sub-section {padding-left: 15px;}
\r
23 div.sub-sub-section {padding-left: 30px;}
\r
24 h1 {font-size: 22px; margin-top: 5px; margin-bottom: 5px;}
\r
25 h2 {font-size: 20px; float: left; margin-top: 15px; margin-bottom: 5px;}
\r
26 h3 {font-size: 18px; float: left; margin-top: 15px; margin-bottom: 5px;}
\r
27 h4 {font-size: 16px; float: left; margin-top: 15px; margin-bottom: 5px;}
\r
28 hr {margin-top: 15px; margin-bottom: 5px;}
\r
29 input, textarea {font-family: 'Bitstream vera sans mono', 'Courier New', 'Courier', monospace;}
\r
30 p.subtle {color: gray; padding: 0; padding-top: 10px; margin: 0;}
\r
31 p.subtle a, p.subtle a:visited {color: #6699cc;}
\r
32 span.item-no {color: black;}
\r
33 span.subtle {color: gray; margin: 0; padding:0;}
\r
34 span.subtle a, span.subtle a:visited {color: #6699cc;}
\r
35 span.term {font-family: 'Bitstream vera sans mono', 'Courier New', 'Courier', monospace;}
\r
36 span.toc-item {color: black;}
\r
37 span.totop {float: right; margin-top: 15px; margin-bottom: 5px;}
\r
38 span.totop a, span.totop a:visited {color: #6699cc;}
\r
39 @media screen { /* fixes for old IE */
\r
40 * html, * html body {overflow-y: auto!important; height: 100%; margin: 0; padding: 0;}
\r
41 * html div#body {height: 100%; overflow-y: auto; position: relative;}
\r
42 * html div#toc {position: absolute;}
\r
46 <title>htmLawed documentation | htmLawed PHP software is a free, open-source, customizable HTML input purifier and filter</title>
50 <h1><a id="peak" name="peak"></a>htmLawed documentation</h1>
52 <div id="toc"><span class="toc-item"><a href="#s1"><span class="item-no">1</span>  About htmLawed</a></span><br />
53   <span class="toc-item"><a href="#s1.1"><span class="item-no">1.1</span>  Example uses</a></span><br />
54   <span class="toc-item"><a href="#s1.2"><span class="item-no">1.2</span>  Features</a></span><br />
55   <span class="toc-item"><a href="#s1.3"><span class="item-no">1.3</span>  History</a></span><br />
56   <span class="toc-item"><a href="#s1.4"><span class="item-no">1.4</span>  License & copyright</a></span><br />
57   <span class="toc-item"><a href="#s1.5"><span class="item-no">1.5</span>  Terms used here</a></span><br />
58   <span class="toc-item"><a href="#s1.6"><span class="item-no">1.6</span>  Availability</a></span><br />
59 <span class="toc-item"><a href="#s2"><span class="item-no">2</span>  Usage</a></span><br />
60   <span class="toc-item"><a href="#s2.1"><span class="item-no">2.1</span>  Simple</a></span><br />
61   <span class="toc-item"><a href="#s2.2"><span class="item-no">2.2</span>  Configuring htmLawed using the <span class="term">$config</span> argument</a></span><br />
62   <span class="toc-item"><a href="#s2.3"><span class="item-no">2.3</span>  Extra HTML specifications using the <span class="term">$spec</span> argument</a></span><br />
63   <span class="toc-item"><a href="#s2.4"><span class="item-no">2.4</span>  Performance time & memory usage</a></span><br />
64   <span class="toc-item"><a href="#s2.5"><span class="item-no">2.5</span>  Some security risks to keep in mind</a></span><br />
65   <span class="toc-item"><a href="#s2.6"><span class="item-no">2.6</span>  Use with <span class="term">kses()</span> code</a></span><br />
66   <span class="toc-item"><a href="#s2.7"><span class="item-no">2.7</span>  Tolerance for ill-written HTML</a></span><br />
67   <span class="toc-item"><a href="#s2.8"><span class="item-no">2.8</span>  Limitations & work-arounds</a></span><br />
68   <span class="toc-item"><a href="#s2.9"><span class="item-no">2.9</span>  Examples of usage</a></span><br />
69 <span class="toc-item"><a href="#s3"><span class="item-no">3</span>  Details</a></span><br />
70   <span class="toc-item"><a href="#s3.1"><span class="item-no">3.1</span>  Invalid/dangerous characters</a></span><br />
71   <span class="toc-item"><a href="#s3.2"><span class="item-no">3.2</span>  Character references/entities</a></span><br />
72   <span class="toc-item"><a href="#s3.3"><span class="item-no">3.3</span>  HTML elements</a></span><br />
73     <span class="toc-item"><a href="#s3.3.1"><span class="item-no">3.3.1</span>  HTML comments & <span class="term">CDATA</span> sections</a></span><br />
74     <span class="toc-item"><a href="#s3.3.2"><span class="item-no">3.3.2</span>  Tag-transformation for better compliance with standards</a></span><br />
75     <span class="toc-item"><a href="#s3.3.3"><span class="item-no">3.3.3</span>  Tag balancing & proper nesting</a></span><br />
76     <span class="toc-item"><a href="#s3.3.4"><span class="item-no">3.3.4</span>  Elements requiring child elements</a></span><br />
77     <span class="toc-item"><a href="#s3.3.5"><span class="item-no">3.3.5</span>  Beautify or compact HTML</a></span><br />
78   <span class="toc-item"><a href="#s3.4"><span class="item-no">3.4</span>  Attributes</a></span><br />
79     <span class="toc-item"><a href="#s3.4.1"><span class="item-no">3.4.1</span>  Auto-addition of XHTML-required attributes</a></span><br />
80     <span class="toc-item"><a href="#s3.4.2"><span class="item-no">3.4.2</span>  Duplicate/invalid <span class="term">id</span> values</a></span><br />
81     <span class="toc-item"><a href="#s3.4.3"><span class="item-no">3.4.3</span>  URL schemes & scripts in attribute values</a></span><br />
82     <span class="toc-item"><a href="#s3.4.4"><span class="item-no">3.4.4</span>  Absolute & relative URLs</a></span><br />
83     <span class="toc-item"><a href="#s3.4.5"><span class="item-no">3.4.5</span>  Lower-cased, standard attribute values</a></span><br />
84     <span class="toc-item"><a href="#s3.4.6"><span class="item-no">3.4.6</span>  Transformation of deprecated attributes</a></span><br />
85     <span class="toc-item"><a href="#s3.4.7"><span class="item-no">3.4.7</span>  Anti-spam & <span class="term">href</span></a></span><br />
86     <span class="toc-item"><a href="#s3.4.8"><span class="item-no">3.4.8</span>  Inline style properties</a></span><br />
87     <span class="toc-item"><a href="#s3.4.9"><span class="item-no">3.4.9</span>  Hook function for tag content</a></span><br />
88   <span class="toc-item"><a href="#s3.5"><span class="item-no">3.5</span>  Simple configuration directive for most valid XHTML</a></span><br />
89   <span class="toc-item"><a href="#s3.6"><span class="item-no">3.6</span>  Simple configuration directive for most <em>safe</em> HTML</a></span><br />
90   <span class="toc-item"><a href="#s3.7"><span class="item-no">3.7</span>  Using a hook function</a></span><br />
91   <span class="toc-item"><a href="#s3.8"><span class="item-no">3.8</span>  Obtaining <em>finalized</em> parameter values</a></span><br />
92   <span class="toc-item"><a href="#s3.9"><span class="item-no">3.9</span>  Retaining non-HTML tags in input with mixed markup</a></span><br />
93 <span class="toc-item"><a href="#s4"><span class="item-no">4</span>  Other</a></span><br />
94   <span class="toc-item"><a href="#s4.1"><span class="item-no">4.1</span>  Support</a></span><br />
95   <span class="toc-item"><a href="#s4.2"><span class="item-no">4.2</span>  Known issues</a></span><br />
96   <span class="toc-item"><a href="#s4.3"><span class="item-no">4.3</span>  Change-log</a></span><br />
97   <span class="toc-item"><a href="#s4.4"><span class="item-no">4.4</span>  Testing</a></span><br />
98   <span class="toc-item"><a href="#s4.5"><span class="item-no">4.5</span>  Upgrade, & old versions</a></span><br />
99   <span class="toc-item"><a href="#s4.6"><span class="item-no">4.6</span>  Comparison with <span class="term">HTMLPurifier</span></a></span><br />
100   <span class="toc-item"><a href="#s4.7"><span class="item-no">4.7</span>  Use through application plug-ins/modules</a></span><br />
101   <span class="toc-item"><a href="#s4.8"><span class="item-no">4.8</span>  Use in non-PHP applications</a></span><br />
102   <span class="toc-item"><a href="#s4.9"><span class="item-no">4.9</span>  Donate</a></span><br />
103   <span class="toc-item"><a href="#s4.10"><span class="item-no">4.10</span>  Acknowledgements</a></span><br />
104 <span class="toc-item"><a href="#s5"><span class="item-no">5</span>  Appendices</a></span><br />
105   <span class="toc-item"><a href="#s5.1"><span class="item-no">5.1</span>  Characters discouraged in HTML</a></span><br />
106   <span class="toc-item"><a href="#s5.2"><span class="item-no">5.2</span>  Valid attribute-element combinations</a></span><br />
107   <span class="toc-item"><a href="#s5.3"><span class="item-no">5.3</span>  CSS 2.1 properties accepting URLs</a></span><br />
108   <span class="toc-item"><a href="#s5.4"><span class="item-no">5.4</span>  Microsoft Windows 1252 character replacements</a></span><br />
109   <span class="toc-item"><a href="#s5.5"><span class="item-no">5.5</span>  URL format</a></span><br />
110   <span class="toc-item"><a href="#s5.6"><span class="item-no">5.6</span>  Brief on htmLawed code</a></span></div><!-- ended div toc -->
114 <div class="comment">htmLawed_README.txt, 12 September 2017<br />
115 htmLawed 1.2.4.1, 12 September 2017<br />
116 Copyright Santosh Patnaik<br />
117 Dual licensed with LGPL 3 and GPL 2+<br />
118 A PHP Labware internal utility - <a href="http://www.bioinformatics.org/phplabware/internal_utilities/htmLawed">http://www.bioinformatics.org/phplabware/internal_utilities/htmLawed</a> </div>
121 <div class="section"><h2>
122 <a name="s1" id="s1"></a><span class="item-no">1</span>  About htmLawed
123 </h2><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
125   htmLawed is a PHP script to process text with HTML markup to make it more compliant with HTML standards and with administrative policies. It works by making HTML well-formed with balanced and properly nested tags, neutralizing code that introduces a security vulnerability or is used for cross-site scripting (XSS) attacks, allowing only specified HTML tags and attributes, and so on. Such <em>lawing in</em> of HTML code ensures that it is in accordance with the aesthetics, safety and usability requirements set by administrators.<br />
127   htmLawed is highly customizable, and fast with low memory usage. Its free and open-source code is in one small file. It does not require extensions or libraries, and works in older versions of PHP as well. It is a good alternative to the HTML <a href="http://tidy.sourceforge.net">Tidy</a> application.<br />
129 <div class="sub-section"><h3>
130 <a name="s1.1" id="s1.1"></a><span class="item-no">1.1</span>  Example uses
131 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
133   *  Filtering of text submitted as comments on blogs to allow only certain HTML elements<br />
135   *  Making RSS newsfeed items standard-compliant: often one uses an excerpt from an HTML document for the content, and with unbalanced tags, non-numerical entities, etc., such excerpts may not be XML-compliant<br />
137   *  Beautifying or pretty-printing HTML code<br />
139   *  Text processing for stricter XML standard-compliance: e.g., to have lowercased <span class="term">x</span> in hexadecimal numeric entities becomes necessary if an HTML document with MathML content needs to be served as <span class="term">application/xml</span><br />
141   *  Scraping text from web-pages<br />
143   *  Transforming an HTML element to another<br />
146 <div class="sub-section"><h3>
147 <a name="s1.2" id="s1.2"></a><span class="item-no">1.2</span>  Features
148 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
150   Key: <span class="term">*</span> security feature, <span class="term">^</span> standard compliance, <span class="term">~</span> requires setting right options<br />
152   htmLawed:<br />
154   *  makes input more <strong>secure</strong> and <strong>standard-compliant</strong> for HTML as well as generic <strong>XML</strong> documents  ^<br />
155   *  supports markup for <strong>HTML 5</strong> and <strong>microdata, ARIA, Ruby, custom attributes</strong>, etc.  ^<br />
156   *  can <strong>beautify</strong> or <strong>compact</strong> HTML  ~<br />
157   *  works with input of almost any <strong>character encoding</strong> and does not affect it<br />
158   *  has good <strong>tolerance for ill-written HTML</strong><br />
160   *  can enforce <strong>restricted use of elements</strong>  *~<br />
161   *  ensures proper closure of empty elements like <span class="term">img</span>  ^<br />
162   *  <strong>transforms deprecated elements</strong> like <span class="term">font</span>  ^~<br />
163   *  can permit HTML <strong>comments</strong> and <strong>CDATA</strong> sections  ^~<br />
164   *  can permit all elements, including <span class="term">script</span>, <span class="term">object</span> and <span class="term">form</span>  ~<br />
166   *  can <strong>restrict attributes by element</strong>  ^~<br />
167   *  removes <strong>invalid attributes</strong>  ^<br />
168   *  lower-cases element and attribute names  ^<br />
169   *  provides <strong>required attributes</strong>, like <span class="term">alt</span> for <span class="term">image</span>  ^<br />
170   *  <strong>transforms deprecated attributes</strong>  ^~<br />
171   *  ensures attributes are <strong>declared only once</strong>  ^<br />
172   *  permits <strong>custom</strong>, non-standard attributes as well as custom rules for standard attributes  ~<br />
174   *  declares value for <em>empty</em> (<em>minimized</em> or <em>boolean</em>) attributes like <span class="term">checked</span>  ^<br />
175   *  checks for potentially dangerous attribute values  *~<br />
176   *  ensures <strong>unique</strong> <span class="term">id</span> attribute values  ^~<br />
177   *  <strong>double-quotes</strong> attribute values  ^<br />
178   *  lower-cases <strong>standard attribute values</strong> like <span class="term">password</span>  ^<br />
180   *  can restrict <strong>URL protocol/scheme by attribute</strong>  *~<br />
181   *  can disable <strong>dynamic expressions</strong> in <span class="term">style</span> values  *~<br />
183   *  neutralizes invalid named <strong>character entities</strong>  ^<br />
184   *  converts hexadecimal numeric entities to decimal ones, or vice versa  ^~<br />
185   *  converts named entities to numeric ones for generic XML use  ^~<br />
187   *  removes <strong>null</strong> characters  *<br />
188   *  neutralizes potentially dangerous proprietary Netscape <strong>Javascript entities</strong>  *<br />
189   *  replaces potentially dangerous <strong>soft-hyphen</strong> character in URL-accepting attribute values with spaces  *<br />
191   *  removes common <strong>invalid characters</strong> not allowed in HTML or XML  ^<br />
192   *  replaces <strong>characters from Microsoft applications</strong> like <span class="term">Word</span> that are discouraged in HTML or XML  ^~<br />
193   *  neutralize entities for characters invalid or discouraged in HTML or XML  ^<br />
194   *  appropriately neutralize <span class="term"><</span>, <span class="term">&</span>, <span class="term">"</span>, and <span class="term">></span> characters  ^*<br />
196   *  understands improperly spaced tag content (e.g., spread over more than a line) and properly spaces them<br />
197   *  attempts to <strong>balance tags</strong> for well-formedness  ^~<br />
198   *  understands when <strong>omitable closing tags</strong> like <span class="term"></p></span> are missing  ^~<br />
199   *  attempts to permit only <strong>validly nested tags</strong>  ^~<br />
200   *  can <strong>either remove or neutralize bad content</strong> ^~<br />
201   *  attempts to <strong>rectify common errors of plain-text misplacement</strong> (e.g., directly inside <span class="term">blockquote</span>) ^~<br />
203   *  has optional <strong>anti-spam</strong> measures such as addition of <span class="term">rel="nofollow"</span> and link-disabling  ~<br />
204   *  optionally makes <strong>relative URLs absolute</strong>, and vice versa  ~<br />
206   *  optionally marks <span class="term">&</span> to identify the entities for <span class="term">&</span>, <span class="term"><</span> and <span class="term">></span> introduced by it  ~<br />
208   *  allows deployment of powerful <strong>hook functions</strong> to <strong>inject</strong> HTML, <strong>consolidate</strong> <span class="term">style</span> attributes to <span class="term">class</span>, finely check attribute values, etc.  ~<br />
211 <div class="sub-section"><h3>
212 <a name="s1.3" id="s1.3"></a><span class="item-no">1.3</span>  History
213 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
215   htmLawed was created in 2007 for use with <span class="term">LabWiki</span>, a wiki software developed at PHP Labware, as a suitable software could not be found. Existing PHP software like <span class="term">Kses</span> and <span class="term">HTMLPurifier</span> were deemed inadequate, slow, resource-intensive, or dependent on an extension or external application like <span class="term">HTML Tidy</span>. The core logic of htmLawed, that of identifying HTML elements and attributes, was based on the <span class="term">Kses</span> (version 0.2.2) HTML filter software of Ulf Harnhammar (it can still be used with code that uses <span class="term">Kses</span>; see <a href="#s2.6">section 2.6</a>.). Support for HTML version 5 was added in May 2013 in a beta and in February 2017 in a production release.<br />
217   See <a href="#s4.3">section 4.3</a> for a detailed log of changes in htmLawed over the years, and <a href="#s4.10">section 4.10</a> for acknowledgements.<br />
220 <div class="sub-section"><h3>
221 <a name="s1.4" id="s1.4"></a><span class="item-no">1.4</span>  License & copyright
222 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
224   htmLawed is free and open-source software, copyrighted by Santosh Patnaik, MD, PhD, and dual-licensed with LGPL version <a href="http://www.gnu.org/licenses/lgpl-3.0.txt">3</a>, and GPL version <a href="http://www.gnu.org/licenses/gpl-2.0.txt">2</a> (or later) licenses.<br />
227 <div class="sub-section"><h3>
228 <a name="s1.5" id="s1.5"></a><span class="item-no">1.5</span>  Terms used here
229 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
231   In this document, only HTML body-level elements are considered. htmLawed does not have support for head-level elements, <span class="term">body</span>, and the frame-level elements, <span class="term">frameset</span>, <span class="term">frame</span> and <span class="term">noframes</span>, and these elements are ignored here.<br />
233   *  <em>administrator</em> - or admin; person setting up the code that utilizes htmLawed; also, <em>user</em><br />
234   *  <em>attributes</em> - name-value pairs like <span class="term">href="http://x.com"</span> in opening tags<br />
235   *  <em>author</em> - see <em>writer</em><br />
236   *  <em>character</em> - atomic unit of text; internally represented by a numeric <em>code-point</em> as specified by the <em>encoding</em> or <em>charset</em> in use<br />
237   *  <em>entity</em> - markup like <span class="term">&gt;</span> and <span class="term">&#160;</span> used to refer to a character<br />
238   *  <em>element</em> - HTML element like <span class="term">a</span> and <span class="term">img</span><br />
239   *  <em>element content</em> -  content between the opening and closing tags of an element, like <span class="term">click</span> of the <span class="term"><a href="x">click</a></span> element<br />
240   *  <em>HTML</em> - implies XHTML unless specified otherwise<br />
241   *  <em>HTML body</em> - content in the <em>body</em> container of an HTML document<br />
242   *  <em>input</em> - text given to htmLawed to process<br />
243   *  <em>legal</em> â€“ standard-compliant; also, <em>valid</em><br />
244   *  <em>processing</em> - involves filtering, correction, etc., of input<br />
245   *  <em>safe</em> - absence or reduction of certain characters and HTML elements and attributes in HTML of text that can otherwise potentially, and circumstantially, expose text readers to security vulnerabilities like cross-site scripting attacks (XSS)<br />
246   *  <em>scheme</em> - a URL protocol like <span class="term">http</span> and <span class="term">ftp</span><br />
247   *  <em>specification</em> - detailed description including rules that define HTML<br />
248   *  <em>standard</em> â€“ widely accepted specification<br />
249   *  <em>style property</em> - terms like <span class="term">border</span> and <span class="term">height</span> for which declarations are made in values for the <span class="term">style</span> attribute of elements<br />
250   *  <em>tag</em> - markers like <span class="term"><a href="x"></span> and <span class="term"></a></span> delineating element content; the opening tag can contain attributes<br />
251   *  <em>tag content</em> - consists of tag markers <span class="term"><</span> and <span class="term">></span>, element names like <span class="term">div</span>, and possibly attributes<br />
252   *  <em>user</em> - administrator<br />
253   *  <em>valid</em> - see <em>legal</em><br />
254   *  <em>writer</em> - end-user like a blog commenter providing the input that is to be processed; also, <em>author</em><br />
255   *  <em>XHTML</em> - XML-compliant HTML; parsing rules for XHTML are more strict than for regular HTML<br />
258 <div class="sub-section"><h3>
259 <a name="s1.6" id="s1.6"></a><span class="item-no">1.6</span>  Availability
260 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
262   htmLawed can be downloaded for free at its <a href="http://www.bioinformatics.org/phplabware/internal_utilities/htmLawed">website</a>. Besides the <span class="term">htmLawed.php</span> file, the download has the htmLawed documentation (this document) in plain <a href="htmLawed_README.txt">text</a> and <a href="htmLawed_README.htm">HTML</a> formats, a script for <a href="htmLawedTest.php">testing</a>, and a text file for <a href="htmLawed_TESTCASE.txt">test-cases</a>. htmLawed is also available as a PHP class (OOP code) at its website.<br />
266 <div class="section"><h2>
267 <a name="s2" id="s2"></a><span class="item-no">2</span>  Usage
268 </h2><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
270   htmLawed works in PHP version 4.4 or higher. Either <span class="term">include()</span> the <span class="term">htmLawed.php</span> file, or copy-paste the entire code.<br />
272   To use with PHP 4.3, have the following code included:<br />
275 <code class="code">    if(!function_exists('ctype_digit')){</code>
278 <code class="code">     function ctype_digit($var){</code>
281 <code class="code">      return ((int) $var == $var);</code>
284 <code class="code">     }</code>
287 <code class="code">    }</code>
290 <div class="sub-section"><h3>
291 <a name="s2.1" id="s2.1"></a><span class="item-no">2.1</span>  Simple
292 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
294   The input text to be processed, <span class="term">$text</span>, is passed as an argument of type string; <span class="term">htmLawed()</span> returns the processed string:<br />
297 <code class="code">    $processed = htmLawed($text);</code>
300   With the <span class="term">htmLawed class</span> (<a href="#s1.6">section 1.6</a>), usage is:<br />
303 <code class="code">    $processed = htmLawed::hl($text);</code>
306   <strong>Notes</strong>: (1) If input is from a <span class="term">$_GET</span> or <span class="term">$_POST</span> value, and <span class="term">magic quotes</span> are enabled on the PHP setup, run <span class="term">stripslashes()</span> on the input before passing to htmLawed. (2) htmLawed does not have support for head-level elements, <span class="term">body</span>, and the frame-level elements, <span class="term">frameset</span>, <span class="term">frame</span> and <span class="term">noframes</span>.<br />
308   By default, htmLawed will process the text allowing all valid HTML elements/tags and commonly used URL schemes and CSS style properties. It will allow Javascript code, <span class="term">CDATA</span> sections and HTML comments, balance tags, and ensure proper nesting of elements. Such actions can be configured using two other optional arguments -- <span class="term">$config</span> and <span class="term">$spec</span>:<br />
311 <code class="code">    $processed = htmLawed($text, $config, $spec);</code>
314   The <span class="term">$config</span> and <span class="term">$spec</span> arguments are detailed below. Some examples are shown in <a href="#s2.9">section 2.9</a>. For maximum protection against <span class="term">XSS</span> and other security vulnerabilities, consider using the <span class="term">safe</span> parameter; see <a href="#s3.6">section 3.6</a>.<br />
317 <div class="sub-section"><h3>
318 <a name="s2.2" id="s2.2"></a><span class="item-no">2.2</span>  Configuring htmLawed using the <span class="term">$config</span> argument
319 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
321   <span class="term">$config</span> instructs htmLawed on how to tackle certain tasks. When <span class="term">$config</span> is not specified, or not set as an array (e.g., <span class="term">$config = 1</span>), htmLawed will take default actions. One or many of the task-action or parameter-value pairs can be specified in <span class="term">$config</span> as array key-value pairs. If a parameter is not specified, htmLawed will use the default value for it, indicated further below. In PHP code, parameter values that are integers should not be quoted and should be used as numeric types (unless meant as string/text). Thus, for instance:<br />
324 <code class="code">    $config = array('comment'=>0, 'cdata'=>1, 'elements'=>'a, b, strong');</code>
327 <code class="code">    $processed = htmLawed($text, $config);</code>
330   Below are the various parameters that can be specified in <span class="term">$config</span>.<br />
332   Key: <span class="term">*</span> default, <span class="term">^</span> different from htmLawed versions below 1.2, <span class="term">~</span> different default when <span class="term">valid_xhtml</span> is set to <span class="term">1</span> (see <a href="#s3.5">section 3.5</a>), <span class="term">"</span> different default when <span class="term">safe</span> is set to <span class="term">1</span> (see <a href="#s3.6">section 3.6</a>)<br />
334   <strong>abs_url</strong><br />
335   Make URLs absolute or relative; <span class="term">$config["base_url"]</span> needs to be set; see <a href="#s3.4.4">section 3.4.4</a><br />
337   <span class="term">-1</span> - make relative<br />
338   <span class="term">0</span> - no action  *<br />
339   <span class="term">1</span> - make absolute<br />
341   <strong>and_mark</strong><br />
342   Mark <span class="term">&</span> characters in the original input; see <a href="#s3.2">section 3.2</a><br />
344   <strong>anti_link_spam</strong><br />
345   Anti-link-spam measure; see <a href="#s3.4.7">section 3.4.7</a><br />
347   <span class="term">0</span> - no measure taken  *<br />
348   <em>array("regex1", "regex2")</em> - will ensure a <span class="term">rel</span> attribute with <span class="term">nofollow</span> in its value in case the <span class="term">href</span> attribute value matches the regular expression pattern <span class="term">regex1</span>, and/or will remove <span class="term">href</span> if its value matches the regular expression pattern <span class="term">regex2</span>. E.g., <span class="term">array("/./", "/://\W*(?!(abc\.com|xyz\.org))/")</span>; see <a href="#s3.4.7">section 3.4.7</a> for more.<br />
350   <strong>anti_mail_spam</strong><br />
351   Anti-mail-spam measure; see <a href="#s3.4.7">section 3.4.7</a><br />
353   <span class="term">0</span> - no measure taken  *<br />
354   <em>word</em> - <span class="term">@</span> in mail address in <span class="term">href</span> attribute value is replaced with specified <em>word</em><br />
356   <strong>balance</strong><br />
357   Balance tags for well-formedness and proper nesting; see <a href="#s3.3.3">section 3.3.3</a><br />
359   <span class="term">0</span> - no<br />
360   <span class="term">1</span> - yes  *<br />
362   <strong>base_url</strong><br />
363   Base URL value that needs to be set if <span class="term">$config["abs_url"]</span> is not <span class="term">0</span>; see <a href="#s3.4.4">section 3.4.4</a><br />
365   <strong>cdata</strong><br />
366   Handling of <span class="term">CDATA</span> sections; see <a href="#s3.3.1">section 3.3.1</a><br />
368   <span class="term">0</span> - don't consider <span class="term">CDATA</span> sections as markup and proceed as if plain text  "<br />
369   <span class="term">1</span> - remove<br />
370   <span class="term">2</span> - allow, but neutralize any <span class="term"><</span>, <span class="term">></span>, and <span class="term">&</span> inside by converting them to named entities<br />
371   <span class="term">3</span> - allow  *<br />
373   <strong>clean_ms_char</strong><br />
374   Replace <em>discouraged</em> characters introduced by Microsoft Word, etc.; see <a href="#s3.1">section 3.1</a><br />
376   <span class="term">0</span> - no  *<br />
377   <span class="term">1</span> - yes<br />
378   <span class="term">2</span> - yes, but replace special single & double quotes with ordinary ones<br />
380   <strong>comment</strong><br />
381   Handling of HTML comments; see <a href="#s3.3.1">section 3.3.1</a><br />
383   <span class="term">0</span> - don't consider comments as markup and proceed as if plain text  "<br />
384   <span class="term">1</span> - remove<br />
385   <span class="term">2</span> - allow, but neutralize any <span class="term"><</span>, <span class="term">></span>, and <span class="term">&</span> inside by converting to named entities<br />
386   <span class="term">3</span> - allow  *<br />
388   <strong>css_expression</strong><br />
389   Allow dynamic CSS expression by not removing the expression from CSS property values in <span class="term">style</span> attributes; see <a href="#s3.4.8">section 3.4.8</a><br />
391   <span class="term">0</span> - remove  *<br />
392   <span class="term">1</span> - allow<br />
394   <strong>deny_attribute</strong><br />
395   Denied HTML attributes; see <a href="#s3.4">section 3.4</a><br />
397   <span class="term">0</span> - none  *<br />
398   <em>string</em> - dictated by values in <em>string</em><br />
399   <span class="term">on*</span> - on* event attributes like <span class="term">onfocus</span> not allowed  "<br />
401   <strong>direct_nest_list</strong><br />
402   Allow direct nesting of a list within another without requiring it to be a list item; see <a href="#s3.3.4">section 3.3.4</a><br />
404   <span class="term">0</span> - no  *<br />
405   <span class="term">1</span> - yes<br />
407   <strong>elements</strong><br />
408   Allowed HTML elements; see <a href="#s3.3">section 3.3</a><br />
410   <em>all</em> - *^<br />
411   <span class="term">* -acronym -big -center -dir -font -isindex -s -strike -tt</span> -  ~^<br />
412   <em>applet, audio, canvas, embed, iframe, object, script, and video elements not allowed</em> -  "^<br />
414   <strong>hexdec_entity</strong><br />
415   Allow hexadecimal numeric entities and do not convert to the more widely accepted decimal ones, or convert decimal to hexadecimal ones; see <a href="#s3.2">section 3.2</a><br />
417   <span class="term">0</span> - no<br />
418   <span class="term">1</span> - yes  *<br />
419   <span class="term">2</span> - convert decimal to hexadecimal ones<br />
421   <strong>hook</strong><br />
422   Name of an optional hook function to alter the input string, <span class="term">$config</span> or <span class="term">$spec</span> before htmLawed enters the main phase of its work; see <a href="#s3.7">section 3.7</a><br />
424   <span class="term">0</span> - no hook function  *<br />
425   <em>name</em> - <em>name</em> is name of the hook function<br />
427   <strong>hook_tag</strong><br />
428   Name of an optional hook function to alter tag content finalized by htmLawed; see <a href="#s3.4.9">section 3.4.9</a><br />
430   <span class="term">0</span> - no hook function  *<br />
431   <em>name</em> - <em>name</em> is name of the hook function<br />
433   <strong>keep_bad</strong><br />
434   Neutralize <em>bad</em> tags by converting their <span class="term"><</span> and <span class="term">></span> characters to entities, or remove them; see <a href="#s3.3.3">section 3.3.3</a><br />
436   <span class="term">0</span> - remove<br />
437   <span class="term">1</span> - neutralize both tags and element content<br />
438   <span class="term">2</span> - remove tags but neutralize element content<br />
439   <span class="term">3</span> and <span class="term">4</span> - like <span class="term">1</span> and <span class="term">2</span> but remove if text (<span class="term">pcdata</span>) is invalid in parent element<br />
440   <span class="term">5</span> and <span class="term">6</span> * -  like <span class="term">3</span> and <span class="term">4</span> but line-breaks, tabs and spaces are left<br />
442   <strong>lc_std_val</strong><br />
443   For XHTML compliance, predefined, standard attribute values, like <span class="term">get</span> for the <span class="term">method</span> attribute of <span class="term">form</span>, must be lowercased; see <a href="#s3.4.5">section 3.4.5</a><br />
445   <span class="term">0</span> - no<br />
446   <span class="term">1</span> - yes  *<br />
448   <strong>make_tag_strict</strong><br />
449   Transform or remove these deprecated HTML elements, even if they are allowed by the admin: acronym, applet, big, center, dir, font, isindex, s, strike, tt; see <a href="#s3.3.2">section 3.3.2</a><br />
451   <span class="term">0</span> - no<br />
452   <span class="term">1</span> - yes, but leave <span class="term">applet</span> and <span class="term">isindex</span> that currently cannot be transformed  *^<br />
453   <span class="term">2</span> - yes, removing <span class="term">applet</span> and <span class="term">isindex</span> elements and their contents (nested elements remain)  ~^<br />
455   <strong>named_entity</strong><br />
456   Allow non-universal named HTML entities, or convert to numeric ones; see <a href="#s3.2">section 3.2</a><br />
458   <span class="term">0</span> - convert<br />
459   <span class="term">1</span> - allow  *<br />
461   <strong>no_deprecated_attr</strong><br />
462   Allow deprecated attributes or transform them; see <a href="#s3.4.6">section 3.4.6</a><br />
464   <span class="term">0</span> - allow<br />
465   <span class="term">1</span> - transform, but <span class="term">name</span> attributes for <span class="term">a</span> and <span class="term">map</span> are retained  *<br />
466   <span class="term">2</span> - transform<br />
468   <strong>parent</strong><br />
469   Name of the parent element, possibly imagined, that will hold the input; see <a href="#s3.3">section 3.3</a><br />
471   <strong>safe</strong><br />
472   Magic parameter to make input the most secure against vulnerabilities like XSS without needing to specify other relevant <span class="term">$config</span> parameters; see <a href="#s3.6">section 3.6</a><br />
474   <span class="term">0</span> - no  *<br />
475   <span class="term">1</span> - will auto-adjust other relevant <span class="term">$config</span> parameters (indicated by <span class="term">"</span> in this list)  ^<br />
477   <strong>schemes</strong><br />
478   Array of attribute-specific, comma-separated, lower-cased list of schemes (protocols) allowed in attributes accepting URLs (or <span class="term">!</span> to <em>deny</em> any URL); <span class="term">*</span> covers all unspecified attributes; see <a href="#s3.4.3">section 3.4.3</a><br />
480   <span class="term">href: aim, app, feed, file, ftp, gopher, http, https, javascript, irc, mailto, news, nntp, sftp, ssh, tel, telnet; *:data, file, http, https, javascript</span>  *^<br />
481   <span class="term">href: aim, feed, file, ftp, gopher, http, https, irc, mailto, news, nntp, sftp, ssh, tel, telnet; style: !; *:file, http, https</span>  "<br />
483   <strong>show_setting</strong><br />
484   Name of a PHP variable to assign the <em>finalized</em> <span class="term">$config</span> and <span class="term">$spec</span> values; see <a href="#s3.8">section 3.8</a><br />
486   <strong>style_pass</strong><br />
487   Ignore <span class="term">style</span> attribute values, letting them through without any alteration<br />
489   <span class="term">0</span> - no *<br />
490   <span class="term">1</span> - htmLawed will let through any <span class="term">style</span> value; see <a href="#s3.4.8">section 3.4.8</a><br />
492   <strong>tidy</strong><br />
493   Beautify or compact HTML code; see <a href="#s3.3.5">section 3.3.5</a><br />
495   <span class="term">-1</span> - compact<br />
496   <span class="term">0</span> - no  *<br />
497   <span class="term">1</span> or <em>string</em> - beautify (custom format specified by <span class="term">string</span>)<br />
499   <strong>unique_ids</strong><br />
500   <span class="term">id</span> attribute value checks; see <a href="#s3.4.2">section 3.4.2</a><br />
502   <span class="term">0</span> - no<br />
503   <span class="term">1</span> - remove duplicate and/or invalid ones  *<br />
504   <em>word</em> - remove invalid ones and replace duplicate ones with new and unique ones based on the <em>word</em>; the admin-specified <em>word</em> cannot contain a space character<br />
506   <strong>valid_xhtml</strong><br />
507   Magic parameter to make input the most valid XHTML without needing to specify other relevant <span class="term">$config</span> parameters; see <a href="#s3.5">section 3.5</a><br />
509   <span class="term">0</span> - no  *<br />
510   <span class="term">1</span> - will auto-adjust other relevant <span class="term">$config</span> parameters (indicated by <span class="term">~</span> in this list)<br />
512   <strong>xml:lang</strong><br />
513   Auto-add <span class="term">xml:lang</span> attribute; see <a href="#s3.4.1">section 3.4.1</a><br />
515   <span class="term">0</span> - no  *<br />
516   <span class="term">1</span> - add if <span class="term">lang</span> attribute is present<br />
517   <span class="term">2</span> - add if <span class="term">lang</span> attribute is present, and remove <span class="term">lang</span>  ~<br />
520 <div class="sub-section"><h3>
521 <a name="s2.3" id="s2.3"></a><span class="item-no">2.3</span>  Extra HTML specifications using the $spec parameter
522 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
524   The <span class="term">$spec</span> argument of htmLawed can be used to disallow an otherwise legal attribute for an element, or to restrict the attribute's values. This can also be helpful as a security measure (e.g., in certain versions of browsers, certain values can cause buffer overflows and denial of service attacks), or in enforcing admin policies. <span class="term">$spec</span> is specified as a string of text containing one or more <em>rules</em>, with multiple rules separated from each other by a semi-colon (<span class="term">;</span>). E.g.,<br />
527 <code class="code">    $spec = 'i=-*; td, tr=style, id, -*; a=id(match="/[a-z][a-z\d.:\-`"]*/i"/minval=2), href(maxlen=100/minlen=34); img=-width,-alt';</code>
530 <code class="code">    $processed = htmLawed($text, $config, $spec);</code>
536 <code class="code">    $processed = htmLawed($text, $config, 'i=-*; td, tr=style, id, -*; a=id(match="/[a-z][a-z\d.:\-`"]*/i"/minval=2), href(maxlen=100/minlen=34); img=-width,-alt');</code>
539   A rule begins with an HTML <strong>element</strong> name(s) (<em>rule-element</em>), for which the rule applies, followed by an equal-to (=) sign. A rule-element may represent multiple elements if comma (,)-separated element names are used. E.g., <span class="term">th,td,tr=</span>.<br />
541   Rest of the rule consists of comma-separated HTML <strong>attribute names</strong>. A minus (-) character before an attribute means that the attribute is not permitted inside the rule-element. E.g., <span class="term">-width</span>. To deny all attributes, <span class="term">-*</span> can be used.<br />
543   Following shows examples of rule excerpts with rule-element <span class="term">a</span> and the attributes that are being permitted:<br />
545   *  <span class="term">a=</span> - all<br />
546   *  <span class="term">a=id</span> - all<br />
547   *  <span class="term">a=href, title, -id, -onclick</span> - all except <span class="term">id</span> and <span class="term">onclick</span><br />
548   *  <span class="term">a=*, id, -id</span> - all except <span class="term">id</span><br />
549   *  <span class="term">a=-*</span> - none<br />
550   *  <span class="term">a=-*, href, title</span> - none except <span class="term">href</span> and <span class="term">title</span><br />
551   *  <span class="term">a=-*, -id, href, title</span> - none except <span class="term">href</span> and <span class="term">title</span><br />
553   Rules regarding <strong>attribute values</strong> are optionally specified inside round brackets after attribute names in solidus (/)-separated <em>parameter = value</em> pairs. E.g., <span class="term">title(maxlen=30/minlen=5)</span>. None or one or more of the following parameters may be specified:<br />
555   *  <span class="term">oneof</span> - one or more choices separated by <span class="term">|</span> that the value should match; if only one choice is provided, then the value must match that choice; matching is case-sensitive<br />
557   *  <span class="term">noneof</span> - one or more choices separated by <span class="term">|</span> that the value should not match; matching is case-sensitive<br />
559   *  <span class="term">maxlen</span> and <span class="term">minlen</span> - upper and lower limits for the number of characters in the attribute value; specified in numbers<br />
561   *  <span class="term">maxval</span> and <span class="term">minval</span> - upper and lower limits for the numerical value specified in the attribute value; specified in numbers<br />
563   *  <span class="term">match</span> and <span class="term">nomatch</span> - pattern that the attribute value should or should not match; specified as PHP/PCRE-compatible regular expressions with delimiters and possibly modifiers (e.g., to specify case-sensitivity for matching)<br />
565   *  <span class="term">default</span> - a value to force on the attribute if the value provided by the writer does not fit any of the specified parameters<br />
567   If <span class="term">default</span> is not set and the attribute value does not satisfy any of the specified parameters, then the attribute is removed. The <span class="term">default</span> value can also be used to force all attribute declarations to take the same value (by getting the values declared illegal by setting, e.g., <span class="term">maxlen</span> to <span class="term">-1</span>).<br />
569   Examples with <em>input</em> <span class="term"><input title="WIDTH" value="10em" /><input title="length" value="5" class="ic1 ic2" /></span> are shown below.<br />
571   <em>Rule</em>: <span class="term">input=title(maxlen=60/minlen=6), value</span><br />
572   <em>Output</em>: <span class="term"><input value="10em" /><input title="length" value="5" class="ic1 ic2" /></span><br />
574   <em>Rule</em>: <span class="term">input=title(), value(maxval=8/default=6)</span><br />
575   <em>Output</em>: <span class="term"><input title="WIDTH" value="6" /><input title="length" value="5" class="ic1 ic2" /></span><br />
577   <em>Rule</em>: <span class="term">input=title(nomatch=%w.d%i), value(match=%em%/default=6em)</span><br />
578   <em>Output</em>: <span class="term"><input value="10em" /><input title="length" value="6em" class="ic1 ic2" /></span><br />
580   <em>Rule</em>: <span class="term">input=class(noneof=ic2|ic3/oneof=ic1|ic4), title(oneof=height|depth/default=depth), value(noneof=5|6)</span><br />
581   <em>Output</em>: <span class="term"><input title="depth" value="10em" /><input title="depth" class="ic1" /></span><br />
583   <strong>Special characters</strong>: The characters <span class="term">;</span>, <span class="term">,</span>, <span class="term">/</span>, <span class="term">(</span>, <span class="term">)</span>, <span class="term">|</span>, <span class="term">~</span> and space have special meanings in the rules. Words in the rules that use such characters, or the characters themselves, should be <em>escaped</em> by enclosing in pairs of double-quotes (<span class="term">"</span>). A back-tick (<span class="term">`</span>) can be used to escape a literal <span class="term">"</span>. An example rule illustrating this is <span class="term">input=value(maxlen=30/match="/^\w/"/default="your `"ID`"")</span>.<br />
585   <strong>Attributes that accept multiple values</strong>: If an attribute is <span class="term">accesskey</span>, <span class="term">class</span>, <span class="term">itemtype</span> or <span class="term">rel</span>, which can have multiple, space-separated values, or <span class="term">srcset</span>, which can have multiple, comma-separated values, htmLawed will parse the attribute value for such multiple values and will individually test each of them.<br />
587   <strong>Note</strong>: To deny an attribute for all elements for which it is legal, <span class="term">$config["deny_attribute"]</span> (see <a href="#s3.4">section 3.4</a>) can be used instead of <span class="term">$spec</span>. Also, attributes can be allowed element-specifically through <span class="term">$spec</span> while being denied globally through <span class="term">$config["deny_attribute"]</span>. The <span class="term">hook_tag</span> parameter (<a href="#s3.4.9">section 3.4.9</a>) can also be possibly used to implement a functionality like that achieved using <span class="term">$spec</span> functionality.<br />
589   <strong>Note</strong>: Attributes' specifications for an element may be set through multiple rules. In case of conflict, the attribute specification in the first rule will get precedence.<br />
591   <span class="term">$spec</span> can also be used to permit custom, non-standard attributes as well as custom rules for standard attributes. Thus, the following value of <span class="term">$spec</span> will permit the custom uses of the standard <span class="term">rel</span> attribute in <span class="term">input</span> (not permitted as per standards) and of a non-standard attribute, <span class="term">vFlag</span>, in <span class="term">img</span>.<br />
594 <code class="code">    $spec = 'img=vFlag; input=rel'</code>
597   The attribute names must begin with an alphabet and cannot have space, equal-to (=) and solidus (/) characters.<br />
600 <div class="sub-section"><h3>
601 <a name="s2.4" id="s2.4"></a><span class="item-no">2.4</span>  Performance time & memory usage
602 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
604   The time and memory consumed during text processing by htmLawed depends on its configuration, the size of the input, and the amount, nestedness and well-formedness of the HTML markup within the input. In particular, tag balancing and beautification each can increase the processing time by about a quarter.<br />
606   The htmLawed <a href="htmLawedTest.php">demo</a> can be used to evaluate the performance and effects of different types of input and <span class="term">$config</span>.<br />
609 <div class="sub-section"><h3>
610 <a name="s2.5" id="s2.5"></a><span class="item-no">2.5</span>  Some security risks to keep in mind
611 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
613   When setting the parameters/arguments (like those to allow certain HTML elements) for use with htmLawed, one should bear in mind that the setting may let through potentially <em>dangerous</em> HTML code which is meant to steal user-data, deface a website, render a page non-functional, etc. Unless end-users, either people or software, supplying the content are completely trusted, security issues arising from the degree of HTML usage permitted through htmLawed's setting should be considered. For example, following increase security risks:<br />
615   *  Allowing <span class="term">script</span>, <span class="term">applet</span>, <span class="term">embed</span>, <span class="term">iframe</span>, <span class="term">canvas</span>, <span class="term">audio</span>, <span class="term">video</span> or <span class="term">object</span> elements, or certain of their attributes like <span class="term">allowscriptaccess</span><br />
617   *  Allowing HTML comments (some Internet Explorer versions are vulnerable with, e.g., <span class="term"><!--[if gte IE 4]><script>alert("xss");</script><![endif]--></span><br />
619   *  Allowing dynamic CSS expressions (some Internet Explorer versions are vulnerable)<br />
621   *  Allowing the <span class="term">style</span> attribute<br />
623   To remove <em>unsecure</em> HTML, code-developers using htmLawed must set <span class="term">$config</span> appropriately. E.g., <span class="term">$config["elements"] = "* -script"</span> to deny the <span class="term">script</span> element (<a href="#s3.3">section 3.3</a>), <span class="term">$config["safe"] = 1</span> to auto-configure ceratin htmLawed parameters for maximizing security (<a href="#s3.6">section 3.6</a>), etc.<br />
625   Permitting the <span class="term">*style*</span> attribute brings in risks of <em>click-jacking</em>, <em>phishing</em>, web-page overlays, etc., <em>even</em> when the <span class="term">safe</span> parameter is enabled (see <a href="#s3.6">section 3.6</a>). Except for URLs and a few other things like CSS dynamic expressions, htmLawed currently does not check every CSS style property. It does provide ways for the code-developer implementing htmLawed to do such checks through htmLawed's <span class="term">$spec</span> argument, and through the <span class="term">hook_tag</span> parameter (see <a href="#s3.4.8">section 3.4.8</a> for more). Disallowing <span class="term">style</span> completely and relying on CSS classes and stylesheet files is recommended.<br />
627   htmLawed does not check or correct the character <strong>encoding</strong> of the input it receives. In conjunction with permissive circumstances, such as when the character encoding is left undefined through HTTP headers or HTML <span class="term">meta</span> tags, this can allow for an exploit (like Google's <em>UTF-7/XSS</em> vulnerability of the past).<br />
629   Ocassionally, though very rarely, the default settings with which htmLawed runs may change between different versions of htmLawed. Admins should keep this in mind when upgrading htmLawed. Important changes in htmLawed's default behavior in new releases of the software are noted in <a href="#s4.5">section 4.5</a> on upgrades.<br />
632 <div class="sub-section"><h3>
633 <a name="s2.6" id="s2.6"></a><span class="item-no">2.6</span>  Use with <span class="term">kses()</span> code
634 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
636   The <span class="term">Kses</span> PHP script for HTML filtering is used by many applications (like <span class="term">WordPress</span>, as in year 2012). It is possible to have such applications use htmLawed instead, since it is compatible with code that calls the <span class="term">kses()</span> function declared in the <span class="term">Kses</span> file (usually named <span class="term">kses.php</span>). E.g., application code like this will continue to work after replacing <span class="term">Kses</span> with htmLawed:<br />
639 <code class="code">    $comment_filtered = kses($comment_input, array('a'=>array(), 'b'=>array(), 'i'=>array()));</code>
642   If the application uses a <span class="term">Kses</span> file that has the <span class="term">kses()</span> function declared, then, to have the application use htmLawed instead of <span class="term">Kses</span>, rename <span class="term">htmLawed.php</span> (to <span class="term">kses.php</span>, e.g.) and replace the <span class="term">Kses</span> file (or just replace the code in the <span class="term">Kses</span> file with the htmLawed code). If the <span class="term">kses()</span> function in the <span class="term">Kses</span> file had been renamed by the application developer (e.g., in <span class="term">WordPress</span>, it is named <span class="term">wp_kses()</span>), then appropriately rename the <span class="term">kses()</span> function in the htmLawed code. Then, add the following code (which was a part of htmLawed prior to version 1.2):<br />
645 <code class="code">    // kses compatibility</code>
648 <code class="code">    function kses($t, $h, $p=array('http', 'https', 'ftp', 'news', 'nntp', 'telnet', 'gopher', 'mailto')){</code>
651 <code class="code">     foreach($h as $k=>$v){</code>
654 <code class="code">      $h[$k]['n']['*'] = 1;</code>
657 <code class="code">     }</code>
660 <code class="code">     $C['cdata'] = $C['comment'] = $C['make_tag_strict'] = $C['no_deprecated_attr'] = $C['unique_ids'] = 0;</code>
663 <code class="code">     $C['keep_bad'] = 1;</code>
666 <code class="code">     $C['elements'] = count($h) ? strtolower(implode(',', array_keys($h))) : '-*';</code>
669 <code class="code">     $C['hook'] = 'kses_hook';</code>
672 <code class="code">     $C['schemes'] = '*:'. implode(',', $p);</code>
675 <code class="code">     return htmLawed($t, $C, $h);</code>
678 <code class="code">     }</code>
682 <code class="code">    function kses_hook($t, &$C, &$S){</code>
685 <code class="code">     return $t;</code>
688 <code class="code">    }</code>
691   If the <span class="term">Kses</span> file used by the application has been significantly altered by the application developers, then one may need a different approach. E.g., with <span class="term">WordPress</span> (as in the year 2012), it is best to copy the htmLawed code, along with the above-mentioned additions, to <span class="term">wp_includes/kses.php</span>, rename the newly added function <span class="term">kses()</span> to <span class="term">wp_kses()</span>, and delete the code for the original <span class="term">wp_kses()</span> function.<br />
693   If the <span class="term">Kses</span> code has a non-empty hook function (e.g., <span class="term">wp_kses_hook()</span> in case of <span class="term">WordPress</span>), then the code for htmLawed's <span class="term">kses_hook()</span> function should be appropriately edited. However, the requirement of the hook function should be re-evaluated considering that htmLawed has extra capabilities. With <span class="term">WordPress</span>, the hook function is an essential one. The following code is suggested for the htmLawed <span class="term">kses_hook()</span> in case of <span class="term">WordPress</span>:<br />
696 <code class="code">    // kses compatibility</code>
699 <code class="code">    function kses_hook($string, &$cf, &$spec){</code>
702 <code class="code">     $allowed_html = $spec;</code>
705 <code class="code">     $allowed_protocols = array();</code>
708 <code class="code">     foreach($cf['schemes'] as $v){</code>
711 <code class="code">      foreach($v as $k2=>$v2){</code>
714 <code class="code">       if(!in_array($k2, $allowed_protocols)){</code>
717 <code class="code">        $allowed_protocols[] = $k2;</code>
720 <code class="code">       }</code>
723 <code class="code">      }</code>
726 <code class="code">     }</code>
729 <code class="code">     return wp_kses_hook($string, $allowed_html, $allowed_protocols);</code>
732 <code class="code">    }</code>
736 <div class="sub-section"><h3>
737 <a name="s2.7" id="s2.7"></a><span class="item-no">2.7</span>  Tolerance for ill-written HTML
738 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
740   htmLawed can work with ill-written HTML code in the input. However, HTML that is too ill-written may not be <em>read</em> as HTML, and may therefore get identified as mere plain text. Following statements indicate the degree of <em>looseness</em> that htmLawed can work with, and can be provided in instructions to writers:<br />
742   *  Tags must be flanked by <span class="term"><</span> and <span class="term">></span> with no <span class="term">></span> inside -- any needed <span class="term">></span> should be put in as <span class="term">&gt;</span>. It is possible for tag content (element name and attributes) to be spread over many lines instead of being on one. A space may be present between the tag content and <span class="term">></span>, like <span class="term"><div ></span> and <span class="term"><img / ></span>, but not after the <span class="term"><</span>.<br />
744   *  Element and attribute names need not be lower-cased.<br />
746   *  Attribute string of elements may be liberally spaced with tabs, line-breaks, etc.<br />
748   *  Attribute values may be single- and not double-quoted.<br />
750   *  Left-padding of numeric entities (like, <span class="term">&#0160;</span>, <span class="term">&x07ff;</span>) with <span class="term">0</span> is okay as long as the number of characters between between the <span class="term">&</span> and the <span class="term">;</span> does not exceed 8. All entities must end with <span class="term">;</span> though.<br />
752   *  Named character entities must be properly cased. Thus, <span class="term">&Lt;</span> or <span class="term">&TILDE;</span> will not be recognized as entities and will be <em>neutralized</em>.<br />
754   *  HTML comments should not be inside element tags (they can be between tags), and should begin with <span class="term"><!--</span> and end with <span class="term">--></span>. Characters like <span class="term"><</span>, <span class="term">></span>, and <span class="term">&</span> may be allowed inside depending on <span class="term">$config</span>, but any <span class="term">--></span> inside should be put in as <span class="term">--&gt;</span>. Any <span class="term">--</span> inside will be automatically converted to <span class="term">-</span>, and a space will be added before the <span class="term">--></span> comment-closing marker  unless <span class="term">$config["comments"]</span> is set to <span class="term">4</span> (<a href="#s3.3.1">section 3.3.1</a>).<br />
756   *  <span class="term">CDATA</span> sections should not be inside element tags, and can be in element content only if plain text is allowed for that element. They should begin with <span class="term"><[CDATA[</span> and end with <span class="term">]]></span>. Characters like <span class="term"><</span>, <span class="term">></span>, and <span class="term">&</span> may be allowed inside depending on <span class="term">$config</span>, but any <span class="term">]]></span> inside should be put in as <span class="term">]]&gt;</span>.<br />
758   *  For attribute values, character entities <span class="term">&lt;</span>, <span class="term">&gt;</span> and <span class="term">&amp;</span> should be used instead of characters <span class="term"><</span> and <span class="term">></span>, and <span class="term">&</span> (when <span class="term">&</span> is not part of a character entity). This applies even for Javascript code in values of attributes like <span class="term">onclick</span>.<br />
760   *  Characters <span class="term"><</span>, <span class="term">></span>, <span class="term">&</span> and <span class="term">"</span> that are part of actual Javascript, etc., code in <span class="term">script</span> elements should be used as such and not be put in as entities like <span class="term">&gt;</span>. Otherwise, though the HTML will be valid, the code may fail to work. Further, if such characters have to be used, then they should be put inside <span class="term">CDATA</span> sections.<br />
762   *  Simple instructions like "an opening tag cannot be present between two closing tags" and "nested elements should be closed in the reverse order of how they were opened" can help authors write balanced HTML. If tags are imbalanced, htmLawed will try to balance them, but in the process, depending on <span class="term">$config["keep_bad"]</span>, some code/text may be lost.<br />
764   *  Input authors should be notified of admin-specified allowed elements, attributes, configuration values (like conversion of named entities to numeric ones), etc.<br />
766   *  With <span class="term">$config["unique_ids"]</span> not <span class="term">0</span> and the <span class="term">id</span> attribute being permitted, writers should carefully avoid using duplicate or invalid <span class="term">id</span> values as even though htmLawed will correct/remove the values, the final output may not be the one desired. E.g., when <span class="term"><a id="home"></a><input id="home" /><label for="home"></label></span> is processed into<br />
767 <span class="term"><a id="home"></a><input id="prefix_home" /><label for="home"></label></span>.<br />
769   *  Even if intended HTML is lost from an ill-written input, the processed output will be more secure and standard-compliant.<br />
771   *  For URLs, unless <span class="term">$config["scheme"]</span> is appropriately set, writers should avoid using escape characters or entities in schemes. E.g., <span class="term">htt&#112;</span> (which many browsers will read as the harmless <span class="term">http</span>) may be considered bad by htmLawed.<br />
773   *  htmLawed will attempt to put plain text present directly inside <span class="term">blockquote</span>, <span class="term">form</span>, <span class="term">map</span> and <span class="term">noscript</span> elements (illegal as per the specifications) inside auto-generated <span class="term">div</span> elements during tag balancing (<a href="#s3.3.3">section 3.3.3</a>).<br />
776 <div class="sub-section"><h3>
777 <a name="s2.8" id="s2.8"></a><span class="item-no">2.8</span>  Limitations & work-arounds
778 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
780   htmLawed's main objective is to make the input text <em>more</em> standard-compliant, secure for readers, and free of HTML elements and attributes considered undesirable by the administrator. Some of its current limitations, regardless of this objective, are noted below along with possible work-arounds.<br />
782   It should be borne in mind that no browser application is 100% standard-compliant, standard specifications continue to evolve, and many browsers accept commonly used non-standard HTML. Regarding security, note that <em>unsafe</em> HTML code is not legally invalid per se.<br />
784   *  By default, htmLawed will not strictly adhere to the <em>current</em> HTML standard. Admins can configure htmLawed to be more strict about standard compliance. Standard specification for HTML is continuously evolving. There are two bodies (<a href="http://www.w3c.org">W3C</a> and <a href="http://www.whatwg.org">WHATWG</a>) that specify the standard and their specifications are not identical. E.g., as in mid-2013, the <span class="term">border</span> attribute is valid in <span class="term">table</span> as per W3C but not WHATWG. Thus, htmLawed may not be fully compliant with the standard of a specific group. The HTML standards/rules that htmLawed uses in its logic are a mix of the W3C and WHATWG standards, and can be lax because of the laxity of HTML interpreters (browsers) regarding standards.<br />
786   *  In general, htmLawed processes input to generate output that is most likely to be standard-compatible in most users' browsers. Thus, for example, it does not enforce the required value of <span class="term">0</span> on <span class="term">border</span> attribute of <span class="term">img</span> (an HTML version 5 specification).<br />
788   *  htmLawed is meant for input that goes into the <span class="term">body</span> of HTML documents. HTML's head-level elements are not supported, nor are the frame-specific elements <span class="term">frameset</span>, <span class="term">frame</span> and <span class="term">noframes</span>. However, content of the latter elements can be individually filtered through htmLawed.<br />
790   *  It cannot handle input that has non-HTML code like <span class="term">SVG</span> and <span class="term">MathML</span>. One way around is to break the input into pieces and passing only those without non-HTML code to htmLawed. Another is described in <a href="#s3.9">section 3.9</a>. A third way may be to some how take advantage of the <span class="term">$config["and_mark"]</span> parameter (see <a href="#s3.2">section 3.2</a>).<br />
792   *  By default, htmLawed won't check many attribute values for standard compliance. E.g., <span class="term">width="20m"</span> with the dimension in non-standard <span class="term">m</span> is let through. Implementing universal and strict attribute value checks can make htmLawed slow and resource-intensive. Admins should look at the <span class="term">hook_tag</span> parameter (<a href="#s3.4.9">section 3.4.9</a>) or <span class="term">$spec</span> to enforce finer checks on attribute values.<br />
794   *  By default, htmLawed considers all ARIA, data-*, event and microdata attributes as global attributes and permits them in all elements. This is not strictly standard-compliant. E.g., the <span class="term">itemtype</span> microdata attribute is permitted only in elements that also have the <span class="term">itemscope</span> attribute. Admins can configure htmLawed to be more strict about this (<a href="#s2.3">section 2.3</a>).<br />
796   *  The attributes, deprecated (which can be transformed too) or not, that it supports are largely those that are in the specifications. Only a few of the proprietary attributes are supported. However, <span class="term">$spec</span> can be used to allow custom attributes (<a href="#s2.3">section 2.3</a>).<br />
798   *  Except for contained URLs and dynamic expressions (also optional), htmLawed does not check CSS style property values. Admins should look at using the <span class="term">hook_tag</span> parameter (<a href="#s3.4.9">section 3.4.9</a>) or <span class="term">$spec</span> for finer checks. Perhaps the best option is to disallow <span class="term">style</span> but allow <span class="term">class</span> attributes with the right <span class="term">oneof</span> or <span class="term">match</span> values for <span class="term">class</span>, and have the various class style properties in <span class="term">.css</span> CSS stylesheet files.<br />
800   *  htmLawed does not parse emoticons, decode <em>BBcode</em>, or <em>wikify</em>, auto-converting text to proper HTML. Similarly, it won't convert line-breaks to <span class="term">br</span> elements. Such functions are beyond its purview. Admins should use other code to pre- or post-process the input for such purposes.<br />
802   *  htmLawed cannot be used to have links force-opened in new windows (by auto-adding appropriate <span class="term">target</span> and <span class="term">onclick</span> attributes to <span class="term">a</span>). Admins should look at Javascript-based DOM-modifying solutions for this. Admins may also be able to use a custom hook function to enforce such checks (<span class="term">hook_tag</span> parameter; see <a href="#s3.4.9">section 3.4.9</a>).<br />
804   *  Nesting-based checks are not possible. E.g., one cannot disallow <span class="term">p</span> elements specifically inside <span class="term">td</span> while permitting it elsewhere. Admins may be able to use a custom hook function to enforce such checks (<span class="term">hook_tag</span> parameter; see <a href="#s3.4.9">section 3.4.9</a>).<br />
806   *  Except for optionally converting absolute or relative URLs to the other type, htmLawed will not alter URLs (e.g., to change the value of query strings or to convert <span class="term">http</span> to <span class="term">https</span>. Having absolute URLs may be a standard-requirement, e.g., when HTML is embedded in email messages, whereas altering URLs for other purposes is beyond htmLawed's goals. Admins may be able to use a custom hook function to enforce such checks (<span class="term">hook_tag</span> parameter; see <a href="#s3.4.9">section 3.4.9</a>).<br />
808   *  Pairs of opening and closing tags that do not enclose any content (like <span class="term"><em></em></span>) are not removed. This may be against the standard specification for certain elements (e.g., <span class="term">table</span>). However, presence of such standard-incompliant code will not break the display or layout of content. Admins can also use simple regex-based code to filter out such code.<br />
810   *  htmLawed does not check for certain element orderings described in the standard specifications (e.g., in a <span class="term">table</span>, <span class="term">tbody</span> is allowed before <span class="term">tfoot</span>). Admins may be able to use a custom hook function to enforce such checks (<span class="term">hook_tag</span> parameter; see <a href="#s3.4.9">section 3.4.9</a>).<br />
812   *  htmLawed does not check the number of nested elements. E.g., it will allow two <span class="term">caption</span> elements in a <span class="term">table</span> element, illegal as per standard specifications. Admins may be able to use a custom hook function to enforce such checks (<span class="term">hook_tag</span> parameter; see <a href="#s3.4.9">section 3.4.9</a>).<br />
814   *  There are multiple ways to interpret ill-written HTML. E.g., in <span class="term"><small><small>text</small></span>, is it that the second closing tag for <span class="term">small</span> is missing or is it that the second opening tag for <span class="term">small</span> was put in by mistake? htmLawed corrects the HTML in the string assuming the former, while the user may have intended the string for the latter. This is an issue that is impossible to address perfectly.<br />
816   *  htmLawed might convert certain entities to actual characters and remove backslashes and CSS comment-markers (<span class="term">/*</span>) in <span class="term">style</span> attribute values in order to detect malicious HTML like crafted, Internet Explorer browser-specific dynamic expressions like <span class="term">&#101;xpression...</span>. If this is too harsh, admins can allow CSS expressions through htmLawed core but then use a custom function through the <span class="term">hook_tag</span> parameter (<a href="#s3.4.9">section 3.4.9</a>) to more specifically identify CSS expressions in the <span class="term">style</span> attribute values. Also, using <span class="term">$config["style_pass"]</span>, it is possible to have htmLawed pass <span class="term">style</span> attribute values without even looking at them (<a href="#s3.4.8">section 3.4.8</a>).<br />
818   *  htmLawed does not correct certain possible attribute-based security vulnerabilities (e.g., <span class="term"><a href="http://x%22+style=%22background-image:xss">x</a></span>). These arise when browsers mis-identify markup in <em>escaped</em> text, defeating the very purpose of escaping text (a bad browser will read the given example as <span class="term"><a href="http://x" style="background-image:xss">x</a></span>).<br />
820   *  Because of poor Unicode support in PHP, htmLawed does not remove the <em>high value</em> HTML-invalid characters with multi-byte code-points. Such characters however are extremely unlikely to be in the input. (see <a href="#s3.1">section 3.1</a>).<br />
822   *  htmLawed does not check or correct the character encoding of the input it receives. In conjunction with permitting circumstances such as when the character encoding is left undefined through HTTP headers or HTML <span class="term">meta</span> tags, this can permit an exploit (like Google's <em>UTF-7/XSS</em> vulnerability of the past). Also, htmLawed can mangle input text if it is not well-formed in terms of character encoding. Administrators can consider using code available elsewhere to check well-formedness of input text characters to correct any defect.<br />
824   *  htmLawed is expected to work with input texts in ASCII standard-compatible single-byte encodings such as national variants of ASCII (like ISO-646-DE/German of the ISO 646 standard), extended ASCII variants (like ISO 8859-10/Turkish of the ISO 8859/ISO Latin standard), ISO 8859-based Windows variants (like Windows 1252), EBCDIC, Shift JIS (Japanese), GB-Roman (Chinese), and KS-Roman (Korean). It should also properly handle texts with variable-byte encodings like UTF-7 (Unicode) and UTF-8 (Unicode). However, htmLawed may mangle input texts with double-byte encodings like UTF-16 (Unicode), JIS X 0208:1997 (Japanese) and K SX 1001:1992 (Korean), or the UTF-32 (Unicode) quadruple-byte encoding. If an input text has such an encoding, administrators can use PHP's <a href="http://php.net/manual/en/book.iconv.php">iconv</a> functions, or some other mean, to convert text to UTF-8 before passing it to htmLawed.<br />
826   *  Like any script using PHP's PCRE regex functions, PHP setup-specific low PCRE limit values can cause htmLawed to at least partially fail with very long input texts.<br />
829 <div class="sub-section"><h3>
830 <a name="s2.9" id="s2.9"></a><span class="item-no">2.9</span>  Examples of usage
831 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
833   Safest, allowing only <em>safe</em> HTML markup --<br />
836 <code class="code">    $config = array('safe'=>1);</code>
839 <code class="code">    $out = htmLawed($in, $config);</code>
842   Simplest, allowing all valid HTML markup including Javascript --<br />
845 <code class="code">    $out = htmLawed($in);</code>
848   Allowing all valid HTML markup but restricting URL schemes in <span class="term">src</span> attribute values to <span class="term">http</span> and <span class="term">https</span> --<br />
851 <code class="code">    $config = array('schemes'=>'*:*; src:http, https');</code>
854 <code class="code">    $out = htmLawed($in, $config);</code>
857   Allowing only <span class="term">safe</span> HTML and the elements <span class="term">a</span>, <span class="term">em</span>, and <span class="term">strong</span> --<br />
860 <code class="code">    $config = array('safe'=>1, 'elements'=>'a, em, strong');</code>
863 <code class="code">    $out = htmLawed($in, $config);</code>
866   Not allowing elements <span class="term">script</span> and <span class="term">object</span> --<br />
869 <code class="code">    $config = array('elements'=>'* -script -object');</code>
872 <code class="code">    $out = htmLawed($in, $config);</code>
875   Not allowing attributes <span class="term">id</span> and <span class="term">style</span> --<br />
878 <code class="code">    $config = array('deny_attribute'=>'id, style');</code>
881 <code class="code">    $out = htmLawed($in, $config);</code>
884   Permitting only attributes <span class="term">title</span> and <span class="term">href</span> --<br />
887 <code class="code">    $config = array('deny_attribute'=>'* -title -href');</code>
890 <code class="code">    $out = htmLawed($in, $config);</code>
893   Remove bad/disallowed tags altogether instead of converting them to entities --<br />
896 <code class="code">    $config = array('keep_bad'=>0);</code>
899 <code class="code">    $out = htmLawed($in, $config);</code>
902   Allowing attribute <span class="term">title</span> only in <span class="term">a</span> and not allowing attributes <span class="term">id</span>, <span class="term">style</span>, or scriptable <em>on*</em> attributes like <span class="term">onclick</span> --<br />
905 <code class="code">    $config = array('deny_attribute'=>'title, id, style, on*');</code>
908 <code class="code">    $spec = 'a=title';</code>
911 <code class="code">    $out = htmLawed($in, $config, $spec);</code>
914   Allowing a custom attribute, <span class="term">vFlag</span>, in <span class="term">img</span> and permitting custom use of the standard attribute, <span class="term">rel</span>, in <span class="term">input</span> --<br />
917 <code class="code">    $spec = 'img=vFlag; input=rel';</code>
920 <code class="code">    $out = htmLawed($in, $config, $spec);</code>
923   Some case-studies are presented below.<br />
925   <strong>1.</strong> A blog administrator wants to allow only <span class="term">a</span>, <span class="term">em</span>, <span class="term">strike</span>, <span class="term">strong</span> and <span class="term">u</span> in comments, but needs <span class="term">strike</span> and <span class="term">u</span> transformed to <span class="term">span</span> for better XHTML 1-strict compliance, and, he wants the <span class="term">a</span> links to point only to <span class="term">http</span> or <span class="term">https</span> resources:<br />
928 <code class="code">    $processed = htmLawed($in, array('elements'=>'a, em, strike, strong, u', 'make_tag_strict'=>1, 'safe'=>1, 'schemes'=>'*:http, https'), 'a=href');</code>
931   <strong>2.</strong> An author uses a custom-made web application to load content on his website. He is the only one using that application and the content he generates has all types of HTML, including scripts. The web application uses htmLawed primarily as a tool to correct errors that creep in while writing HTML and to take care of the occasional <em>bad</em> characters in copy-paste text introduced by Microsoft Office. The web application provides a preview before submitted input is added to the content. For the previewing process, htmLawed is set up as follows:<br />
934 <code class="code">    $processed = htmLawed($in, array('css_expression'=>1, 'keep_bad'=>1, 'make_tag_strict'=>1, 'schemes'=>'*:*', 'valid_xhtml'=>1));</code>
937   For the final submission process, <span class="term">keep_bad</span> is set to <span class="term">6</span>. A value of <span class="term">1</span> for the preview process allows the author to note and correct any HTML mistake without losing any of the typed text.<br />
939   <strong>3.</strong> A data-miner is scraping information in a specific table of similar web-pages and is collating the data rows, and uses htmLawed to reduce unnecessary markup and white-spaces:<br />
942 <code class="code">    $processed = htmLawed($in, array('elements'=>'tr, td', 'tidy'=>-1), 'tr, td =');</code>
947 <div class="section"><h2>
948 <a name="s3" id="s3"></a><span class="item-no">3</span>  Details
949 </h2><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
950 <div class="sub-section"><h3>
951 <a name="s3.1" id="s3.1"></a><span class="item-no">3.1</span>  Invalid/dangerous characters
952 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
954   Valid characters (more correctly, their code-points) in HTML or XML are, hexadecimally, <span class="term">9</span>, <span class="term">a</span>, <span class="term">d</span>, <span class="term">20</span> to <span class="term">d7ff</span>, and <span class="term">e000</span> to <span class="term">10ffff</span>, except <span class="term">fffe</span> and <span class="term">ffff</span> (decimally, <span class="term">9</span>, <span class="term">10</span>, <span class="term">13</span>, <span class="term">32</span> to <span class="term">55295</span>, and <span class="term">57344</span> to <span class="term">1114111</span>, except <span class="term">65534</span> and <span class="term">65535</span>). htmLawed removes the invalid characters <span class="term">0</span> to <span class="term">8</span>, <span class="term">b</span>, <span class="term">c</span>, and <span class="term">e</span> to <span class="term">1f</span>.<br />
956   Because of PHP's poor native support for multi-byte characters, htmLawed cannot check for the remaining invalid code-points. However, for various reasons, it is very unlikely for any of those characters to be in the input.<br />
958   Characters that are discouraged (see <a href="#s5.1">section 5.1</a>) but not invalid are not removed by htmLawed.<br />
960   It (function <span class="term">hl_tag()</span>) also replaces the potentially dangerous (in some Mozilla [Firefox] and Opera browsers) soft-hyphen character (code-point, hexadecimally, <span class="term">ad</span>, or decimally, <span class="term">173</span>) in attribute values with spaces. Where required, the characters <span class="term"><</span>, <span class="term">></span>, <span class="term">&</span>, and <span class="term">"</span> are converted to entities.<br />
962   With <span class="term">$config["clean_ms_char"]</span> set as <span class="term">1</span> or <span class="term">2</span>, many of the discouraged characters (decimal code-points <span class="term">127</span> to <span class="term">159</span> except <span class="term">133</span>) that many Microsoft applications incorrectly use (as per the <span class="term">Windows 1252</span> [<span class="term">Cp-1252</span>] or a similar encoding system), and the character for decimal code-point <span class="term">133</span>, are converted to appropriate decimal numerical entities (or removed for a few cases)-- see appendix in <a href="#s5.4">section 5.4</a>. This can help avoid some display issues arising from copying-pasting of content.<br />
964   With <span class="term">$config["clean_ms_char"]</span> set as <span class="term">2</span>, characters for the hexadecimal code-points <span class="term">82</span>, <span class="term">91</span>, and <span class="term">92</span> (for special single-quotes), and <span class="term">84</span>, <span class="term">93</span>, and <span class="term">94</span> (for special double-quotes) are converted to ordinary single and double quotes respectively and not to entities.<br />
966   The character values are replaced with entities/characters and not character values referred to by the entities/characters to keep this task independent of the character-encoding of input text.<br />
968   The <span class="term">$config["clean_ms_char"]</span> parameter should not be used if authors do not copy-paste Microsoft-created text, or if the input text is not believed to use the <span class="term">Windows 1252</span> (<span class="term">Cp-1252</span>) or a similar encoding like <span class="term">Cp-1251</span> (otherwise, for example when UTF-8 encoding is in use, Japanese or Korean characters can get mangled). Further, the input form and the web-pages displaying it or its content should have the character encoding appropriately marked-up.<br />
971 <div class="sub-section"><h3>
972 <a name="s3.2" id="s3.2"></a><span class="item-no">3.2</span>  Character references/entities
973 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
975   Valid character entities take the form <span class="term">&*;</span> where <span class="term">*</span> is <span class="term">#x</span> followed by a hexadecimal number (hexadecimal numeric entity; like <span class="term">&#xA0;</span> for non-breaking space), or alphanumeric like <span class="term">gt</span> (external or named entity; like <span class="term">&nbsp;</span> for non-breaking space), or <span class="term">#</span> followed by a number (decimal numeric entity; like <span class="term">&#160;</span> for non-breaking space). Character entities referring to the soft-hyphen character (the <span class="term">&shy;</span> or <span class="term">\xad</span> character; hexadecimal code-point <span class="term">ad</span> [decimal <span class="term">173</span>]) in URL-accepting attribute values are always replaced with spaces; soft-hyphens in attribute values introduce vulnerabilities in some older versions of the Opera and Mozilla [Firefox] browsers.<br />
977   htmLawed (function <span class="term">hl_ent()</span>):<br />
979   *  Neutralizes entities with multiple leading zeroes or missing semi-colons (potentially dangerous)<br />
981   *  Lowercases the <span class="term">X</span> (for XML-compliance) and <span class="term">A-F</span> of hexadecimal numeric entities<br />
983   *  Neutralizes entities referring to characters that are HTML-invalid (see <a href="#s3.1">section 3.1</a>)<br />
985   *  Neutralizes entities referring to characters that are HTML-discouraged (code-points, hexadecimally, <span class="term">7f</span> to <span class="term">84</span>, <span class="term">86</span> to <span class="term">9f</span>, and <span class="term">fdd0</span> to <span class="term">fddf</span>, or decimally, <span class="term">127</span> to <span class="term">132</span>, <span class="term">134</span> to <span class="term">159</span>, and <span class="term">64991</span> to <span class="term">64976</span>). Entities referring to the remaining discouraged characters (see <a href="#s5.1">section 5.1</a> for a full list) are let through.<br />
987   *  Neutralizes named entities that are not in the specifications<br />
989   *  Optionally converts valid HTML-specific named entities except <span class="term">&gt;</span>, <span class="term">&lt;</span>, <span class="term">&quot;</span>, and <span class="term">&amp;</span> to decimal numeric ones (hexadecimal if $config["hexdec_entity"] is <span class="term">2</span>) for generic XML-compliance. For this, <span class="term">$config["named_entity"]</span> should be <span class="term">1</span>.<br />
991   *  Optionally converts hexadecimal numeric entities to the more widely supported decimal ones. For this, <span class="term">$config["hexdec_entity"]</span> should be <span class="term">0</span>.<br />
993   *  Optionally converts decimal numeric entities to the hexadecimal ones. For this, <span class="term">$config["hexdec_entity"]</span> should be <span class="term">2</span>.<br />
995   <em>Neutralization</em> refers to the <em>entitification</em> of <span class="term">&</span> to <span class="term">&amp;</span>.<br />
997   <strong>Note</strong>: htmLawed does not convert entities to the actual characters represented by them; one can pass the htmLawed output through PHP's <span class="term">html_entity_decode</span> <a href="http://www.php.net/html_entity_decode">function</a> for that.<br />
999   <strong>Note</strong>: If <span class="term">$config["and_mark"]</span> is set, and set to a value other than <span class="term">0</span>, then the <span class="term">&</span> characters in the original input are replaced with the control character for the hexadecimal code-point <span class="term">6</span> (<span class="term">\x06</span>; <span class="term">&</span> characters introduced by htmLawed, e.g., after converting <span class="term"><</span> to <span class="term">&lt;</span>, are not affected). This allows one to distinguish, say, an <span class="term">&gt;</span> introduced by htmLawed and an <span class="term">&gt;</span> put in by the input writer, and can be helpful in further processing of the htmLawed-processed text (e.g., to identify the character sequence <span class="term">o(><)o</span> to generate an emoticon image). When this feature is active, admins should ensure that the htmLawed output is not directly used in web pages or XML documents as the presence of the <span class="term">\x06</span> can break documents. Before use in such documents, and preferably before any storage, any remaining <span class="term">\x06</span> should be changed back to <span class="term">&</span>, e.g., with:<br />
1002 <code class="code">    $final = str_replace("\x06", '&', $prelim);</code>
1005   Also, see <a href="#s3.9">section 3.9</a>.<br />
1008 <div class="sub-section"><h3>
1009 <a name="s3.3" id="s3.3"></a><span class="item-no">3.3</span>  HTML elements
1010 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1012   htmLawed can be configured to allow only certain HTML elements (tags) in the input. Disallowed elements (just tag-content, and not element-content), based on <span class="term">$config["keep_bad"]</span>, are either <em>neutralized</em> (converted to plain text by entitification of <span class="term"><</span> and <span class="term">></span>) or removed.<br />
1014   E.g., with only <span class="term">em</span> permitted:<br />
1019 <code class="code">      <em>My</em> website is <a href="http://a.com>a.com</a>.</code>
1022   Output, with <span class="term">$config["keep_bad"] = 0</span>:<br />
1025 <code class="code">      <em>My</em> website is a.com.</code>
1028   Output, with <span class="term">$config["keep_bad"]</span> not <span class="term">0</span>:<br />
1031 <code class="code">      <em>My</em> website is &lt;a href=""&gt;a.com&lt;/a&gt;.</code>
1034   See <a href="#s3.3.3">section 3.3.3</a> for differences between the various non-zero <span class="term">$config["keep_bad"]</span> values.<br />
1036   htmLawed by default permits these 118 HTML elements:<br />
1039 <code class="code">    a, abbr, acronym, address, applet, area, article, aside, audio, b, bdi, bdo, big, blockquote, br, button, canvas, caption, center, cite, code, col, colgroup, command, data, datalist, dd, del, details, dfn, dir, div, dl, dt, em, embed, fieldset, figcaption, figure, font, footer, form, h1, h2, h3, h4, h5, h6, header, hgroup, hr, i, iframe, img, input, ins, isindex, kbd, keygen, label, legend, li, link, main, map, mark, menu, meta, meter, nav, noscript, object, ol, optgroup, option, output, p, param, pre, progress, q, rb, rbc, rp, rt, rtc, ruby, s, samp, script, section, select, small, source, span, strike, strong, style, sub, summary, sup, table, tbody, td, textarea, tfoot, th, thead, time, tr, track, tt, u, ul, var, video, wbr</code>
1042   The HTML version 4 elements <span class="term">acronym</span>, <span class="term">applet</span>, <span class="term">big</span>, <span class="term">center</span>, <span class="term">dir</span>, <span class="term">font</span>, <span class="term">strike</span>, and <span class="term">tt</span> are obsolete/deprecated in HTML version 5. On the other hand, the obsolete/deprecated HTML 4 elements <span class="term">embed</span>, <span class="term">menu</span> and <span class="term">u</span> are no longer so in HTML 5. Elements new to HTML 5 are <span class="term">article</span>, <span class="term">aside</span>, <span class="term">audio</span>, <span class="term">bdi</span>, <span class="term">canvas</span>, <span class="term">command</span>, <span class="term">data</span>, <span class="term">datalist</span>, <span class="term">details</span>, <span class="term">figure</span>, <span class="term">figcaption</span>, <span class="term">footer</span>, <span class="term">header</span>, <span class="term">hgroup</span>, <span class="term">keygen</span>, <span class="term">link</span>, <span class="term">main</span>, <span class="term">mark</span>, <span class="term">meta</span>, <span class="term">meter</span>, <span class="term">nav</span>, <span class="term">output</span>, <span class="term">progress</span>, <span class="term">section</span>, <span class="term">source</span>, <span class="term">style</span>, <span class="term">summary</span>, <span class="term">time</span>, <span class="term">track</span>, <span class="term">video</span>, and <span class="term">wbr</span>. The <span class="term">link</span>, <span class="term">meta</span> and <span class="term">style</span> elements exist in HTML 4 but are not allowed in the HTML body. These 16 elements are <em>empty</em> elements that have an opening tag with possible content but no element content (thus, no closing tag): <span class="term">area</span>, <span class="term">br</span>, <span class="term">col</span>, <span class="term">command</span>, <span class="term">embed</span>, <span class="term">hr</span>, <span class="term">img</span>, <span class="term">input</span>, <span class="term">isindex</span>, <span class="term">keygen</span>, <span class="term">link</span>, <span class="term">meta</span>, <span class="term">param</span>, <span class="term">source</span>, <span class="term">track</span>, and <span class="term">wbr</span>.<br />
1044   With <span class="term">$config["safe"] = 1</span>, the default set will exclude <span class="term">applet</span>, <span class="term">audio</span>, <span class="term">canvas</span>, <span class="term">embed</span>, <span class="term">iframe</span>, <span class="term">object</span>, <span class="term">script</span> and <span class="term">video</span>; see <a href="#s3.6">section 3.6</a>.<br />
1046   When <span class="term">$config["elements"]</span>, which specifies allowed elements, is <em>properly</em> defined, and neither empty nor set to <span class="term">0</span> or <span class="term">*</span>, the default set is not used. To have elements added to or removed from the default set, a <span class="term">+/-</span> notation is used. E.g., <span class="term">*-script-object</span> implies that only <span class="term">script</span> and <span class="term">object</span> are disallowed, whereas <span class="term">*+embed</span> means that <span class="term">noembed</span> is also allowed. Elements can also be specified as comma separated names. E.g., <span class="term">a, b, i</span> means only <span class="term">a</span>, <span class="term">b</span> and <span class="term">i</span> are permitted. In this notation, <span class="term">*</span>, <span class="term">+</span> and <span class="term">-</span> have no significance and can actually cause a mis-reading.<br />
1048   Some more examples of <span class="term">$config["elements"]</span> values indicating permitted elements (note that empty spaces are liberally allowed for clarity):<br />
1050   *  <span class="term">a, blockquote, code, em, strong</span> -- only <span class="term">a</span>, <span class="term">blockquote</span>, <span class="term">code</span>, <span class="term">em</span>, and <span class="term">strong</span><br />
1051   *  <span class="term">*-script</span> -- all excluding <span class="term">script</span><br />
1052   *  <span class="term">* -acronym -big -center -dir -font -isindex -s -strike -tt</span> -- only non-obsolete/deprecated elements of HTML5<br />
1053   *  <span class="term">*+noembed-script</span> -- all including <span class="term">noembed</span> excluding <span class="term">script</span><br />
1055   Some mis-usages (and the resulting permitted elements) that can be avoided:<br />
1057   *  <span class="term">-*</span> -- none; instead of htmLawed, one might just use, e.g., the <span class="term">htmlspecialchars()</span> PHP function<br />
1058   *  <span class="term">*, -script</span> -- all except <span class="term">script</span>; admin probably meant <span class="term">*-script</span><br />
1059   *  <span class="term">-*, a, em, strong</span> -- all; admin probably meant <span class="term">a, em, strong</span><br />
1060   *  <span class="term">*</span> -- all; admin need not have set <span class="term">elements</span><br />
1061   *  <span class="term">*-form+form</span> -- all; a <span class="term">+</span> will always over-ride any <span class="term">-</span><br />
1062   *  <span class="term">*, noembed</span> -- only <span class="term">noembed</span>; admin probably meant <span class="term">*+noembed</span><br />
1063   *  <span class="term">a, +b, i</span> -- only <span class="term">a</span> and <span class="term">i</span>; admin probably meant <span class="term">a, b, i</span><br />
1065   Basically, when using the <span class="term">+/-</span> notation, commas (<span class="term">,</span>) should not be used, and vice versa, and <span class="term">*</span> should be used with the former but not the latter.<br />
1067   <strong>Note</strong>: Even if an element that is not in the default set is allowed through <span class="term">$config["elements"]</span>, like <span class="term">noembed</span> in the last example, it will eventually be removed during tag balancing unless such balancing is turned off (<span class="term">$config["balance"]</span> set to <span class="term">0</span>). Currently, the only way around this, which actually is simple, is to edit htmLawed's PHP code which define various arrays in the function <span class="term">hl_bal()</span> to accommodate the element and its nesting properties.<br />
1069   A possible second way to specify allowed elements is to set <span class="term">$config["parent"]</span> to an element name that supposedly will hold the input, and to set <span class="term">$config["balance"]</span> to <span class="term">1</span>. During tag balancing (see <a href="#s3.3.3">section 3.3.3</a>), all elements that cannot legally nest inside the parent element will be removed. The parent element is auto-reset to <span class="term">div</span> if <span class="term">$config["parent"]</span> is empty, <span class="term">body</span>, or an element not in htmLawed's default set of 118 elements.<br />
1071   <em>Tag transformation</em> is possible for improving compliance with HTML standards -- most of the obsolete/deprecated elements of HTML version 5 are converted to valid  ones; see <a href="#s3.3.2">section 3.3.2</a>.<br />
1073 <div class="sub-sub-section"><h4>
1074 <a name="s3.3.1" id="s3.3.1"></a><span class="item-no">3.3.1</span>  Handling of comments & CDATA sections
1075 </h4><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1077   <span class="term">CDATA</span> sections have the format <span class="term"><![CDATA[...anything but not "]]>"...]]></span>, and HTML comments, <span class="term"><!--...anything but not "-->"... --></span>. Neither HTML comments nor <span class="term">CDATA</span> sections can reside inside tags. HTML comments can exist anywhere else, but <span class="term">CDATA</span> sections can exist only where plain text is allowed (e.g., immediately inside <span class="term">td</span> element content but not immediately inside <span class="term">tr</span> element content).<br />
1079   htmLawed (function <span class="term">hl_cmtcd()</span>) handles HTML comments or <span class="term">CDATA</span> sections depending on the values of <span class="term">$config["comment"]</span> or <span class="term">$config["cdata"]</span>. If <span class="term">0</span>, such markup is not looked for and the text is processed like plain text. If <span class="term">1</span>, it is removed completely. If <span class="term">2</span>, it is preserved but any <span class="term"><</span>, <span class="term">></span> and <span class="term">&</span> inside are changed to entities. If <span class="term">3</span> for <span class="term">$config["cdata"]</span>, or <span class="term">3</span> or <span class="term">4</span> for <span class="term">$config["comment"]</span>, they are left as such. When <span class="term">$config["comment"]</span> is set to <span class="term">4</span>, htmLawed will not force a space character before the <span class="term">--></span> comment-closing marker. While such a space is required for standard-compliance, it can corrupt marker code put in HTML by some software (such as Microsoft Outlook).<br />
1081   Note that for the last two cases, HTML comments and <span class="term">CDATA</span> sections will always be removed from tag content (function <span class="term">hl_tag()</span>).<br />
1083   Examples:<br />
1087 <code class="code">    <!-- home link--><a href="home.htm"><![CDATA[x=&y]]>Home</a></code>
1089   Output (<span class="term">$config["comment"] = 0, $config["cdata"] = 2</span>):<br />
1091 <code class="code">    &lt;-- home link--&gt;<a href="home.htm"><![CDATA[x=&amp;y]]>Home</a></code>
1093   Output (<span class="term">$config["comment"] = 1, $config["cdata"] = 2</span>):<br />
1095 <code class="code">    <a href="home.htm"><![CDATA[x=&amp;y]]>Home</a></code>
1097   Output (<span class="term">$config["comment"] = 2, $config["cdata"] = 2</span>):<br />
1099 <code class="code">    <!-- home link --><a href="home.htm"><![CDATA[x=&amp;y]]>Home</a></code>
1101   Output (<span class="term">$config["comment"] = 2, $config["cdata"] = 1</span>):<br />
1103 <code class="code">    <!-- home link --><a href="home.htm">Home</a></code>
1105   Output (<span class="term">$config["comment"] = 3, $config["cdata"] = 3</span>):<br />
1107 <code class="code">    <!-- home link --><a href="home.htm"><![CDATA[x=&y]]>Home</a></code>
1109   Output (<span class="term">$config["comment"] = 4, $config["cdata"] = 3</span>):<br />
1111 <code class="code">    <!-- home link--><a href="home.htm"><![CDATA[x=&y]]>Home</a></code>
1114   For standard-compliance, comments are given the form <span class="term"><!--comment --></span>, and any <span class="term">--</span> in the content is made <span class="term">-</span>. When <span class="term">$config["comment"]</span> is set to <span class="term">4</span>, htmLawed will not force a space character before the <span class="term">--></span> comment-closing marker.<br />
1116   When <span class="term">$config["safe"] = 1</span>, CDATA sections and comments are considered plain text unless <span class="term">$config["comment"]</span> or <span class="term">$config["cdata"]</span> is explicitly specified; see <a href="#s3.6">section 3.6</a>.<br />
1119 <div class="sub-sub-section"><h4>
1120 <a name="s3.3.2" id="s3.3.2"></a><span class="item-no">3.3.2</span>  Tag-transformation for better compliance with standards
1121 </h4><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1123   If <span class="term">$config["make_tag_strict"]</span> is set and not <span class="term">0</span>, following deprecated elements (and attributes), as per HTML 5 specification, even if admin-permitted, are mutated as indicated (element content remains intact; function <span class="term">hl_tag2()</span>):<br />
1125   *  acronym - <span class="term">abbr</span><br />
1126   *  applet - based on <span class="term">$config["make_tag_strict"]</span>, unchanged (<span class="term">1</span>) or removed (<span class="term">2</span>)<br />
1127   *  big - <span class="term">span style="font-size: larger;"</span><br />
1128   *  center - <span class="term">div style="text-align: center;"</span><br />
1129   *  dir - <span class="term">ul</span><br />
1130   *  font (face, size, color) -    <span class="term">span style="font-family: ; font-size: ; color: ;"</span> (size transformation <a href="http://style.cleverchimp.com/font_size_intervals/altintervals.html">reference</a>)<br />
1131   *  isindex - based on <span class="term">$config["make_tag_strict"]</span>, unchanged (<span class="term">1</span>) or removed (<span class="term">2</span>)<br />
1132   *  s - <span class="term">span style="text-decoration: line-through;"</span><br />
1133   *  strike - <span class="term">span style="text-decoration: line-through;"</span><br />
1134   *  tt - <span class="term">code</span><br />
1136   For an element with a pre-existing <span class="term">style</span> attribute value, the extra style properties are appended.<br />
1138   Example input:<br />
1141 <code class="code">    <center></code>
1144 <code class="code">     The PHP <s>software</s> script used for this <strike>web-page</strike> web-page is <font style="font-weight: bold " face=arial size='+3' color   =  "red  ">htmLawedTest.php</font>, from <u style= 'color:green'>PHP Labware</u>.</code>
1147 <code class="code">    </center></code>
1150   The output:<br />
1153 <code class="code">    <div style="text-align: center;"></code>
1156 <code class="code">     The PHP <span style="text-decoration: line-through;">software</span> script used for this <span style="text-decoration: line-through;">web-page</span> web-page is <span style="font-weight: bold; font-family: arial; color: red; font-size: 200%;">htmLawedTest.php</span>, from <span style="color:green; text-decoration: underline;">PHP Labware</span>.</code>
1159 <code class="code">    </div></code>
1163 <div class="sub-sub-section"><h4>
1164 <a name="s3.3.3" id="s3.3.3"></a><span class="item-no">3.3.3</span>  Tag balancing & proper nesting
1165 </h4><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1167   If <span class="term">$config["balance"]</span> is set to <span class="term">1</span>, htmLawed (function <span class="term">hl_bal()</span>) checks and corrects the input to have properly balanced tags and legal element content (i.e., any element nesting should be valid, and plain text may be present only in the content of elements that allow them).<br />
1169   Depending on the value of <span class="term">$config["keep_bad"]</span> (see <a href="#s2.2">section 2.2</a> and <a href="#s3.3">section 3.3</a>), illegal content may be removed or neutralized to plain text by converting < and > to entities:<br />
1171   <span class="term">0</span> - remove; this option is available only to maintain Kses-compatibility and should not be used otherwise (see <a href="#s2.6">section 2.6</a>)<br />
1172   <span class="term">1</span> - neutralize tags and keep element content<br />
1173   <span class="term">2</span> - remove tags but keep element content<br />
1174   <span class="term">3</span> and <span class="term">4</span> - like <span class="term">1</span> and <span class="term">2</span>, but keep element content only if text (<span class="term">pcdata</span>) is valid in parent element as per specs<br />
1175   <span class="term">5</span> and <span class="term">6</span> -  like <span class="term">3</span> and <span class="term">4</span>, but line-breaks, tabs and spaces are left<br />
1177   Example input (disallowing the <span class="term">p</span> element):<br />
1180 <code class="code">    <*> Pseudo-tags <*></code>
1183 <code class="code">    <xml>Non-HTML tag xml</xml></code>
1186 <code class="code">    <p></code>
1189 <code class="code">    Disallowed tag p</code>
1192 <code class="code">    </p></code>
1195 <code class="code">    <ul>Bad<li>OK</li></ul></code>
1198   The output with <span class="term">$config["keep_bad"] = 1</span>:<br />
1201 <code class="code">    &lt;*&gt; Pseudo-tags &lt;*&gt;</code>
1204 <code class="code">    &lt;xml&gt;Non-HTML tag xml&lt;/xml&gt;</code>
1207 <code class="code">    &lt;p&gt;</code>
1210 <code class="code">    Disallowed tag p</code>
1213 <code class="code">    &lt;/p&gt;</code>
1216 <code class="code">    <ul>Bad<li>OK</li></ul></code>
1219   The output with <span class="term">$config["keep_bad"] = 3</span>:<br />
1222 <code class="code">    &lt;*&gt; Pseudo-tags &lt;*&gt;</code>
1225 <code class="code">    &lt;xml&gt;Non-HTML tag xml&lt;/xml&gt;</code>
1228 <code class="code">    &lt;p&gt;</code>
1231 <code class="code">    Disallowed tag p</code>
1234 <code class="code">    &lt;/p&gt;</code>
1237 <code class="code">    <ul><li>OK</li></ul></code>
1240   The output with <span class="term">$config["keep_bad"] = 6</span>:<br />
1243 <code class="code">    &lt;*&gt; Pseudo-tags &lt;*&gt;</code>
1246 <code class="code">    Non-HTML tag xml</code>
1250 <code class="code">    Disallowed tag p</code>
1254 <code class="code">    <ul><li>OK</li></ul></code>
1257   An option like <span class="term">1</span> is useful, e.g., when a writer previews his submission, whereas one like <span class="term">3</span> is useful before content is finalized and made available to all.<br />
1259   <strong>Note:</strong> In the example above, unlike <span class="term"><*></span>, <span class="term"><xml></span> gets considered as a tag (even though there is no HTML element named <span class="term">xml</span>). Thus, the <span class="term">keep_bad</span> parameter's value affects <span class="term"><xml></span> but not <span class="term"><*></span>. In general, text matching the regular expression pattern <span class="term"><(/?)([a-zA-Z][a-zA-Z1-6]*)([^>]*?)\s?></span> is considered a tag (phrase enclosed by the angled brackets <span class="term"><</span> and <span class="term">></span>, and starting [with an optional slash preceding] with an alphanumeric word that starts with an alphabet...), and is subjected to the <span class="term">keep_bad</span> value.<br />
1261   Nesting/content rules for each of the 118 elements in htmLawed's default set (see <a href="#s3.3">section 3.3</a>) are defined in function <span class="term">hl_bal()</span>. This means that if a non-standard element besides <span class="term">embed</span> is being permitted through <span class="term">$config["elements"]</span>, the element's tag content will end up getting removed if <span class="term">$config["balance"]</span> is set to <span class="term">1</span>.<br />
1263   Plain text and/or certain elements nested inside <span class="term">blockquote</span>, <span class="term">form</span>, <span class="term">map</span> and <span class="term">noscript</span> need to be in block-level elements. This point is often missed during manual writing of HTML code. htmLawed attempts to address this during balancing. E.g., if the parent container is set as <span class="term">form</span>, the input <span class="term">B:<input type="text" value="b" />C:<input type="text" value="c" /></span> is converted to <span class="term"><div>B:<input type="text" value="b" />C:<input type="text" value="c" /></div></span>.<br />
1266 <div class="sub-sub-section"><h4>
1267 <a name="s3.3.4" id="s3.3.4"></a><span class="item-no">3.3.4</span>  Elements requiring child elements
1268 </h4><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1270   As per HTML specifications, elements such as those below require legal child elements nested inside them:<br />
1273 <code class="code">    blockquote, dir, dl, form, map, menu, noscript, ol, optgroup, rbc, rtc, ruby, select, table, tbody, tfoot, thead, tr, ul</code>
1276   In some cases, the specifications stipulate the number and/or the ordering of the child elements. A <span class="term">table</span> can have 0 or 1 <span class="term">caption</span>, <span class="term">tbody</span>, <span class="term">tfoot</span>, and <span class="term">thead</span>, but they must be in this order: <span class="term">caption</span>, <span class="term">thead</span>, <span class="term">tfoot</span>, <span class="term">tbody</span>.<br />
1278   htmLawed currently does not check for conformance to these rules. Note that any non-compliance in this regard will not introduce security vulnerabilities, crash browser applications, or affect the rendering of web-pages.<br />
1280   With <span class="term">$config["direct_list_nest"]</span> set to <span class="term">1</span>, htmLawed will allow direct nesting of <span class="term">ol</span>, <span class="term">ul</span>, or <span class="term">menu</span> list within another <span class="term">ol</span>, <span class="term">ul</span>, or <span class="term">menu</span> without requiring the child list to be within an <span class="term">li</span> of the parent list. While this may not be standard-compliant, directly nested lists are rendered properly by almost all browsers. The parameter <span class="term">$config["direct_list_nest"]</span> has no effect if tag balancing (<a href="#s3.3.3">section 3.3.3</a>) is turned off.<br />
1283 <div class="sub-sub-section"><h4>
1284 <a name="s3.3.5" id="s3.3.5"></a><span class="item-no">3.3.5</span>  Beautify or compact HTML
1285 </h4><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1287   By default, htmLawed will neither <em>beautify</em> HTML code by formatting it with indentations, etc., nor will it make it compact by removing un-needed white-space.(It does always properly white-space tag content.)<br />
1289   As per the HTML standards, spaces, tabs and line-breaks in web-pages (except those inside <span class="term">pre</span> elements) are all considered equivalent, and referred to as <em>white-spaces</em>. Browser applications are supposed to consider contiguous white-spaces as just a single space, and to disregard white-spaces trailing opening tags or preceding closing tags. This white-space <em>normalization</em> allows the use of text/code beautifully formatted with indentations and line-spacings for readability. Such <em>pretty</em> HTML can, however, increase the size of web-pages, or make the extraction or scraping of plain text cumbersome.<br />
1291   With the <span class="term">$config</span> parameter <span class="term">tidy</span>, htmLawed can be used to beautify or compact the input text. Input with just plain text and no HTML markup is also subject to this. Besides <span class="term">pre</span>, the <span class="term">script</span> and <span class="term">textarea</span> elements, CDATA sections, and HTML comments are not subjected to the tidying process.<br />
1293   To <em>compact</em>, use <span class="term">$config["tidy"] = -1</span>; single instances or runs of white-spaces are replaced with a single space, and white-spaces trailing and leading open and closing tags, respectively, are removed.<br />
1295   To <em>beautify</em>, <span class="term">$config["tidy"]</span> is set as <span class="term">1</span>, or for customized tidying, as a string like <span class="term">2s2n</span>. The <span class="term">s</span> or <span class="term">t</span> character specifies the use of spaces or tabs for indentation. The first and third characters, any of the digits 0-9, specify the number of spaces or tabs per indentation, and any parental lead spacing (extra indenting of the whole block of input text). The <span class="term">r</span> and <span class="term">n</span> characters are used to specify line-break characters: <span class="term">n</span> for <span class="term">\n</span> (Unix/Mac OS X line-breaks), <span class="term">rn</span> or <span class="term">nr</span> for <span class="term">\r\n</span> (Windows/DOS line-breaks), or <span class="term">r</span> for <span class="term">\r</span>.<br />
1297   The <span class="term">$config["tidy"]</span> value of <span class="term">1</span> is equivalent to <span class="term">2s0n</span>. Other <span class="term">$config["tidy"]</span> values are read loosely: a value of <span class="term">4</span> is equivalent to <span class="term">4s0n</span>; <span class="term">t2</span>, to <span class="term">1t2n</span>; <span class="term">s</span>, to <span class="term">2s0n</span>; <span class="term">2TR</span>, to <span class="term">2t0r</span>; <span class="term">T1</span>, to <span class="term">1t1n</span>; <span class="term">nr3</span>, to <span class="term">3s0nr</span>, and so on. Except in the indentations and line-spacings, runs of white-spaces are replaced with a single space during beautification.<br />
1299   Input formatting using <span class="term">$config["tidy"]</span> is not recommended when input text has mixed markup (like HTML + PHP).<br />
1302 <div class="sub-section"><h3>
1303 <a name="s3.4" id="s3.4"></a><span class="item-no">3.4</span>  Attributes
1304 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1306   In its default setting, htmLawed will only permit attributes described in the HTML specifications (including deprecated ones). A list of the attributes and the elements they are allowed in is in <a href="#s5.2">section 5.2</a>. Using the <span class="term">$spec</span> argument, htmLawed can be forced to permit custom, non-standard attributes as well as custom rules for standard attributes (<a href="#s2.3">section 2.3</a>).<br />
1308   Custom <em>data-*</em> (<em>data-star</em>) attributes, where the first three characters of the value of <em>star</em> (*) after lower-casing do not equal <span class="term">xml</span>, and the value of <em>star</em> does not have a colon (:), equal-to (=), newline, solidus (/), space or tab character, or any upper-case A-Z character are allowed in all elements. ARIA, event and microdata attributes like <span class="term">aria-live</span>, <span class="term">onclick</span> and <span class="term">itemid</span> are also considered global attributes (<a href="#s5.2">section 5.2</a>).<br />
1310   When <span class="term">$config["deny_attribute"]</span> is not set, or set to <span class="term">0</span>, or empty (<span class="term">""</span>), all attributes are permitted. Otherwise, <span class="term">$config["deny_attribute"]</span> can be set as a list of comma-separated names of the denied attributes. <span class="term">on*</span> can be used to refer to the group of potentially dangerous, script-accepting event attributes like <span class="term">onblur</span> and <span class="term">onchange</span> that have <span class="term">on</span> at the beginning of their names. Similarly, <span class="term">aria*</span> and <span class="term">data*</span> can be used to respectively refer to the set of all ARIA and data-* attributes.<br />
1312   With <span class="term">$config["safe"] = 1</span> (<a href="#s3.6">section 3.6</a>), the <span class="term">on*</span> event attributes are automatically disallowed even if a value for <span class="term">$config["deny_attribute"]</span> has been manually provided.<br />
1314   Note that attributes specified in <span class="term">$config["deny_attribute"]</span> are denied globally, for all elements. To deny attributes for only specific elements, <span class="term">$spec</span> (see <a href="#s2.3">section 2.3</a>) can be used. <span class="term">$spec</span> can also be used to element-specifically permit an attribute otherwise denied through <span class="term">$config["deny_attribute"]</span>.<br />
1316   Finer restrictions on attributes can also be put into effect through <span class="term">$config["deny_attribute"]</span> (<a href="3.4.9">section</a>).<br />
1318   <strong>Note</strong>: To deny all but a few attributes globally, a simpler way to specify <span class="term">$config["deny_attribute"]</span> would be to use the notation <span class="term">* -attribute1 -attribute2 ...</span>. Thus, a value of <span class="term">* -title -href</span> implies that except <span class="term">href</span> and <span class="term">title</span> (where allowed as per standards) all other attributes are to be removed. With this notation, the value for the parameter <span class="term">safe</span> (<a href="#s3.6">section 3.6</a>) will have no effect on <span class="term">deny_attribute</span>. Values of <span class="term">aria*</span> <span class="term">data*</span>, and <span class="term">on*</span> cannot be used in this notation to refer to the sets of all ARIA, data-*, and on* attributes respectively.<br />
1320   htmLawed (function <span class="term">hl_tag()</span>) also:<br />
1322   *  Lower-cases attribute names<br />
1323   *  Removes duplicate attributes (last one stays)<br />
1324   *  Gives attributes the form <span class="term">name="value"</span> and single-spaces them, removing unnecessary white-spacing<br />
1325   *  Provides <em>required</em> attributes (see <a href="#s3.4.1">section 3.4.1</a>)<br />
1326   *  Double-quotes values and escapes any <span class="term">"</span> inside them<br />
1327   *  Replaces the possibly dangerous soft-hyphen characters (hexadecimal code-point <span class="term">ad</span>) in the values with spaces<br />
1328   *  Allows custom function to additionally filter/modify attribute values (see <a href="#s3.4.9">section 3.4.9</a>)<br />
1330 <div class="sub-sub-section"><h4>
1331 <a name="s3.4.1" id="s3.4.1"></a><span class="item-no">3.4.1</span>  Auto-addition of XHTML-required attributes
1332 </h4><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1334   If indicated attributes for the following elements are found missing, htmLawed (function <span class="term">hl_tag()</span>) will add them (with values same as attribute names unless indicated otherwise below):<br />
1336   *  area - alt (<span class="term">area</span>)<br />
1337   *  area, img - src, alt (<span class="term">image</span>)<br />
1338   *  bdo - dir (<span class="term">ltr</span>)<br />
1339   *  form - action<br />
1340   *  label - command<br />
1341   *  map - name<br />
1342   *  optgroup - label<br />
1343   *  param - name<br />
1344   *  style - scoped<br />
1345   *  textarea - rows (<span class="term">10</span>), cols (<span class="term">50</span>)<br />
1347   Additionally, with <span class="term">$config["xml:lang"]</span> set to <span class="term">1</span> or <span class="term">2</span>, if the <span class="term">lang</span> but not the <span class="term">xml:lang</span> attribute is declared, then the latter is added too, with a value copied from that of <span class="term">lang</span>. This is for better standard-compliance. With <span class="term">$config["xml:lang"]</span> set to <span class="term">2</span>, the <span class="term">lang</span> attribute is removed (XHTML specification).<br />
1349   Note that the <span class="term">name</span> attribute for <span class="term">map</span>, invalid in XHTML, is also transformed if required -- see <a href="#s3.4.6">section 3.4.6</a>.<br />
1352 <div class="sub-sub-section"><h4>
1353 <a name="s3.4.2" id="s3.4.2"></a><span class="item-no">3.4.2</span>  Duplicate/invalid <span class="term">id</span> values
1354 </h4><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1356   If <span class="term">$config["unique_ids"]</span> is <span class="term">1</span>, htmLawed (function <span class="term">hl_tag()</span>) removes <span class="term">id</span> attributes with values that are not standards-compliant (must not have a space character) or duplicate. If <span class="term">$config["unique_ids"]</span> is a word (without a non-word character like space), any duplicate but otherwise valid value will be appropriately prefixed with the word to ensure its uniqueness.<br />
1358   Even if multiple inputs need to be filtered (through multiple calls to htmLawed), htmLawed ensures uniqueness of <span class="term">id</span> values as it uses a global variable (<span class="term">$GLOBALS["hl_Ids"]</span> array). Further, an admin can restrict the use of certain <span class="term">id</span> values by presetting this variable before htmLawed is called into use. E.g.:<br />
1361 <code class="code">    $GLOBALS['hl_Ids'] = array('top'=>1, 'bottom'=>1, 'myform'=>1); // id values not allowed in input</code>
1364 <code class="code">    $processed = htmLawed($text); // filter input</code>
1368 <div class="sub-sub-section"><h4>
1369 <a name="s3.4.3" id="s3.4.3"></a><span class="item-no">3.4.3</span>  URL schemes & scripts in attribute values
1370 </h4><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1372   htmLawed edits attributes that take URLs as values if they are found to contain un-permitted schemes. E.g., if the <span class="term">afp</span> scheme is not permitted, then <span class="term"><a href="afp://domain.org"></span> becomes <span class="term"><a href="denied:afp://domain.org"></span>, and if Javascript is not permitted <span class="term"><a onclick="javascript:xss();"></span> becomes <span class="term"><a onclick="denied:javascript:xss();"></span>.<br />
1374   By default htmLawed permits these schemes in URLs for the <span class="term">href</span> attribute:<br />
1377 <code class="code">    aim, app, feed, file, ftp, gopher, http, https, javascript, irc, mailto, news, nntp, sftp, ssh, tel, telnet</code>
1380   Also, only <span class="term">data</span>, <span class="term">file</span>, <span class="term">http</span>, <span class="term">https</span> and <span class="term">javascript</span> are permitted in these attributes that accept URLs:<br />
1383 <code class="code">    action, cite, classid, codebase, data, itemtype, longdesc, model, pluginspage, pluginurl, src, srcset, style, usemap, and event attributes like onclick</code>
1386   With <span class="term">$config["safe"] = 1</span> (<a href="#s3.6">section 3.6</a>), the above is changed to disallow <span class="term">app</span>, <span class="term">data</span> and <span class="term">javascript</span>.<br />
1388   These default sets are used when <span class="term">$config["schemes"]</span> is not set (see <a href="#s2.2">section 2.2</a>). To over-ride the defaults, <span class="term">$config["schemes"]</span> is defined as a string of semi-colon-separated sub-strings of type <span class="term">attribute: comma-separated schemes</span>. E.g., <span class="term">href: mailto, http, https; onclick: javascript; src: http, https</span>. For unspecified attributes, <span class="term">data</span>, <span class="term">file</span>, <span class="term">http</span>, <span class="term">https</span> and <span class="term">javascript</span> are permitted. This can be changed by passing schemes for <span class="term">*</span> in <span class="term">$config["schemes"]</span>. E.g., <span class="term">href: mailto, http, https; *: https, https</span>.<br />
1390   <span class="term">*</span> (asterisk) can be put in the list of schemes to permit all protocols. E.g., <span class="term">style: *; img: http, https</span> results in protocols not being checked in <span class="term">style</span> attribute values. However, in such cases, any relative-to-absolute URL conversion, or vice versa, (<a href="#s3.4.4">section 3.4.4</a>) is not done. When an attribute is explicitly listed in <span class="term">$config["schemes"]</span>, then filtering is dictated by the setting for the attribute, with no effect of the setting for asterisk. That is, the set of attributes that asterisk refers to no longer includes the listed attribute.<br />
1392   Thus, <em>to allow the xmpp scheme</em>, one can set <span class="term">$config["schemes"]</span> as <span class="term">href: mailto, http, https; *: http, https, xmpp</span>, or <span class="term">href: mailto, http, https, xmpp; *: http, https, xmpp</span>, or <span class="term">*: *</span>, and so on. The consequence of each of these example values will be different (e.g., only the last two but not the first will allow <span class="term">xmpp</span> in <span class="term">href</span>)<br />
1394   As a side-note, one may find <span class="term">style: *</span> useful as URLs in <span class="term">style</span> attributes can be specified in a variety of ways, and the patterns that htmLawed uses to identify URLs may mistakenly identify non-URL text.<br />
1396   <span class="term">!</span> can be put in the list of schemes to disallow all protocols as well as <em>local</em> URLs. Thus, with <span class="term">href: http, style: !</span>, <span class="term"><a href="http://cnn.com" style="background-image: url(local.jpg);">CNN</a></span> will become <span class="term"><a href="http://cnn.com" style="background-image: url(denied:local.jpg);">CNN</a></span><br />
1398   <strong>Note</strong>: If URL-accepting attributes other than those listed above are being allowed, then the scheme will not be checked unless the attribute name contains the string <span class="term">src</span> (e.g., <span class="term">dynsrc</span>) or starts with <span class="term">o</span> (e.g., <span class="term">onbeforecopy</span>).<br />
1400   With <span class="term">$config["safe"] = 1</span>, all URLs are disallowed in the <span class="term">style</span> attribute values.<br />
1403 <div class="sub-sub-section"><h4>
1404 <a name="s3.4.4" id="s3.4.4"></a><span class="item-no">3.4.4</span>  Absolute & relative URLs in attribute values
1405 </h4><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1407   htmLawed can make absolute URLs in attributes like <span class="term">href</span> relative (<span class="term">$config["abs_url"]</span> is <span class="term">-1</span>), and vice versa (<span class="term">$config["abs_url"]</span> is <span class="term">1</span>). URLs in scripts are not considered for this, and so are URLs like <span class="term">#section_6</span> (fragment), <span class="term">?name=Tim#show</span> (starting with query string), and <span class="term">;var=1?name=Tim#show</span> (starting with parameters). Further, this requires that <span class="term">$config["base_url"]</span> be set properly, with the <span class="term">://</span> and a trailing slash (<span class="term">/</span>), with no query string, etc. E.g., <span class="term">file:///D:/page/</span>, <span class="term">https://abc.com/x/y/</span>, or <span class="term">http://localhost/demo/</span> are okay, but <span class="term">file:///D:/page/?help=1</span>, <span class="term">abc.com/x/y/</span> and <span class="term">http://localhost/demo/index.htm</span> are not.<br />
1409   For making absolute URLs relative, only those URLs that have the <span class="term">$config["base_url"]</span> string at the beginning are converted. E.g., with <span class="term">$config["base_url"] = "https://abc.com/x/y/"</span>, <span class="term">https://abc.com/x/y/a.gif</span> and <span class="term">https://abc.com/x/y/z/b.gif</span> become <span class="term">a.gif</span> and <span class="term">z/b.gif</span> respectively, while <span class="term">https://abc.com/x/c.gif</span> is not changed.<br />
1411   When making relative URLs absolute, only values for scheme, network location (host-name) and path values in the base URL are inherited. See <a href="#s5.5">section 5.5</a> for more about the URL specification as per RFC <a href="http://www.ietf.org/rfc/rfc1808.txt">1808</a>.<br />
1414 <div class="sub-sub-section"><h4>
1415 <a name="s3.4.5" id="s3.4.5"></a><span class="item-no">3.4.5</span>  Lower-cased, standard attribute values
1416 </h4><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1418   Optionally, for standard-compliance, htmLawed (function <span class="term">hl_tag()</span>) lower-cases standard attribute values to give, e.g., <span class="term">input type="password"</span> instead of <span class="term">input type="Password"</span>, if <span class="term">$config["lc_std_val"]</span> is <span class="term">1</span>. Attribute values matching those listed below for any of the elements listed further below (plus those for the <span class="term">type</span> attribute of <span class="term">button</span> or <span class="term">input</span>) are lower-cased:<br />
1421 <code class="code">    all, auto, baseline, bottom, button, captions, center, chapters, char, checkbox, circle, col, colgroup, color, cols, data, date, datetime, datetime-local, default, descriptions, email, file, get, groups, hidden, image, justify, left, ltr, metadata, middle, month, none, number, object, password, poly, post, preserve, radio, range, rect, ref, reset, right, row, rowgroup, rows, rtl, search, submit, subtitles, tel, text, time, top, url, week</code>
1425 <code class="code">    a, area, bdo, button, col, fieldset, form, img, input, object, ol, optgroup, option, param, script, select, table, td, textarea, tfoot, th, thead, tr, track, xml:space</code>
1428   The following <em>empty</em> (<em>minimized</em>) attributes are always assigned lower-cased values (same as the attribute names):<br />
1431 <code class="code">    checkbox, checked, command, compact, declare, defer, default, disabled, hidden, inert, ismap, itemscope, multiple, nohref, noresize, noshade, nowrap, open, radio, readonly, required, reversed, selected</code>
1435 <div class="sub-sub-section"><h4>
1436 <a name="s3.4.6" id="s3.4.6"></a><span class="item-no">3.4.6</span>  Transformation of deprecated attributes
1437 </h4><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1439   If <span class="term">$config["no_deprecated_attr"]</span> is <span class="term">0</span>, then deprecated attributes are removed and, in most cases, their values are transformed to CSS style properties and added to the <span class="term">style</span> attributes (function <span class="term">hl_tag()</span>). Except for <span class="term">bordercolor</span> for <span class="term">table</span>, <span class="term">tr</span> and <span class="term">td</span>, the scores of proprietary attributes that were never part of any cross-browser standard are not supported in this functionality.<br />
1441   *  align in caption, div, h, h2, h3, h4, h5, h6, hr, img, input, legend, object, p, table - for <span class="term">img</span> with value of <span class="term">left</span> or <span class="term">right</span>, becomes, e.g., <span class="term">float: left</span>; for <span class="term">div</span> and <span class="term">table</span> with value <span class="term">center</span>, becomes <span class="term">margin: auto</span>; all others become, e.g., <span class="term">text-align: right</span><br />
1442   *  bgcolor in table, td, th and tr - E.g., <span class="term">bgcolor="#ffffff"</span> becomes <span class="term">background-color: #ffffff</span><br />
1443   *  border in object - E.g., <span class="term">height="10"</span> becomes <span class="term">height: 10px</span><br />
1444   *  bordercolor in table, td and tr - E.g., <span class="term">bordercolor=#999999</span> becomes <span class="term">border-color: #999999;</span><br />
1445   *  compact in dl, ol and ul - <span class="term">font-size: 85%</span><br />
1446   *  cellspacing in table - <span class="term">cellspacing="10"</span> becomes <span class="term">border-spacing: 10px</span><br />
1447   *  clear in br - E.g., 'clear="all" becomes <span class="term">clear: both</span><br />
1448   *  height in td and th - E.g., <span class="term">height= "10"</span> becomes <span class="term">height: 10px</span> and <span class="term">height="*"</span> becomes <span class="term">height: auto</span><br />
1449   *  hspace in img and object - E.g., <span class="term">hspace="10"</span> becomes <span class="term">margin-left: 10px; margin-right: 10px</span><br />
1450   *  language in script - <span class="term">language="VBScript"</span> becomes <span class="term">type="text/vbscript"</span><br />
1451   *  name in a, form, iframe, img and map - E.g., <span class="term">name="xx"</span> becomes <span class="term">id="xx"</span><br />
1452   *  noshade in hr - <span class="term">border-style: none; border: 0; background-color: gray; color: gray</span><br />
1453   *  nowrap in td and th - <span class="term">white-space: nowrap</span><br />
1454   *  size in hr - E.g., <span class="term">size="10"</span> becomes <span class="term">height: 10px</span><br />
1455   *  vspace in img and object - E.g., <span class="term">vspace="10"</span> becomes <span class="term">margin-top: 10px; margin-bottom: 10px</span><br />
1456   *  width in hr, pre, table, td and th - like <span class="term">height</span><br />
1458   Example input:<br />
1461 <code class="code">    <img src="j.gif" alt="image" name="dad's" /><img src="k.gif" alt="image" id="dad_off" name="dad" /></code>
1464 <code class="code">    <br clear="left" /></code>
1467 <code class="code">    <hr noshade size="1" /></code>
1470 <code class="code">    <img name="img" src="i.gif" align="left" alt="image" hspace="10" vspace="10" width="10em" height="20" border="1" style="padding:5px;" /></code>
1473 <code class="code">    <table width="50em" align="center" bgcolor="red"></code>
1476 <code class="code">     <tr></code>
1479 <code class="code">      <td width="20%"></code>
1482 <code class="code">       <div align="center"></code>
1485 <code class="code">        <h3 align="right">Section</h3></code>
1488 <code class="code">        <p align="right">Para</p></code>
1491 <code class="code">       </div></code>
1494 <code class="code">      </td></code>
1497 <code class="code">      <td width="*"></code>
1500 <code class="code">      </td></code>
1503 <code class="code">     </tr></code>
1506 <code class="code">    </table></code>
1509 <code class="code">    <br clear="all" /></code>
1512   And the output with <span class="term">$config["no_deprecated_attr"] = 1</span>:<br />
1515 <code class="code">    <img src="j.gif" alt="image" id="dad's" /><img src="k.gif" alt="image" id="dad_off" /></code>
1518 <code class="code">    <br style="clear: left;" /></code>
1521 <code class="code">    <hr style="border-style: none; border: 0; background-color: gray; color: gray; size: 1px;" /></code>
1524 <code class="code">    <img src="i.gif" alt="image" width="10em" height="20" style="padding:5px; float: left; margin-left: 10px; margin-right: 10px; margin-top: 10px; margin-bottom: 10px; border: 1px;" id="img" /></code>
1527 <code class="code">    <table width="50em" style="margin: auto; background-color: red;"></code>
1530 <code class="code">     <tr></code>
1533 <code class="code">      <td style="width: 20%;"></code>
1536 <code class="code">       <div style="margin: auto;"></code>
1539 <code class="code">        <h3 style="text-align: right;">Section</h3></code>
1542 <code class="code">        <p style="text-align: right;">Para</p></code>
1545 <code class="code">       </div></code>
1548 <code class="code">      </td></code>
1551 <code class="code">      <td style="width: auto;"></code>
1554 <code class="code">      </td></code>
1557 <code class="code">     </tr></code>
1560 <code class="code">    </table></code>
1563 <code class="code">    <br style="clear: both;" /></code>
1566   For <span class="term">lang</span>, deprecated in XHTML 1.1, transformation is taken care of through <span class="term">$config["xml:lang"]</span>; see <a href="#s3.4.1">section 3.4.1</a>.<br />
1568   The attribute <span class="term">name</span> is deprecated in <span class="term">form</span>, <span class="term">iframe</span>, and <span class="term">img</span>, and is replaced with <span class="term">id</span> if an <span class="term">id</span> attribute doesn't exist and if the <span class="term">name</span> value is appropriate for <span class="term">id</span> (i.e., doesn't have a non-word character like space). For such replacements for <span class="term">a</span> and <span class="term">map</span>, for which the <span class="term">name</span> attribute is deprecated in XHTML 1.1, <span class="term">$config["no_deprecated_attr"]</span> should be set to <span class="term">2</span> (when set to <span class="term">1</span>, for these two elements, the <span class="term">name</span> attribute is retained).<br />
1571 <div class="sub-sub-section"><h4>
1572 <a name="s3.4.7" id="s3.4.7"></a><span class="item-no">3.4.7</span>  Anti-spam & <span class="term">href</span>
1573 </h4><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1575   htmLawed (function <span class="term">hl_tag()</span>) can check the <span class="term">href</span> attribute values (link addresses) as an anti-spam (email or link spam) measure.<br />
1577   If <span class="term">$config["anti_mail_spam"]</span> is not <span class="term">0</span>, the <span class="term">@</span> of email addresses in <span class="term">href</span> values like <span class="term">mailto:a@b.com</span> is replaced with text specified by <span class="term">$config["anti_mail_spam"]</span>. The text should be of a form that makes it clear to others that the address needs to be edited before a mail is sent; e.g., <span class="term"><remove_this_antispam>@</span> (makes the example address <span class="term">a<remove_this_antispam>@b.com</span>).<br />
1579   For regular links, one can choose to have a <span class="term">rel</span> attribute with <span class="term">nofollow</span> in its value (which tells some search engines to not follow a link). This can discourage link spammers. Additionally, or as an alternative, one can choose to empty the <span class="term">href</span> value altogether (disable the link).<br />
1581   For use of these options, <span class="term">$config["anti_link_spam"]</span> should be set as an array with values <span class="term">regex1</span> and <span class="term">regex2</span>, both or one of which can be empty (like <span class="term">array("", "regex2")</span>) to indicate that that option is not to be used. Otherwise, <span class="term">regex1</span> or <span class="term">regex2</span> should be PHP- and PCRE-compatible regular expression patterns: <span class="term">href</span> values will be matched against them and those matching the pattern will accordingly be treated.<br />
1583   Note that the regular expressions should have <em>delimiters</em>, and be well-formed and preferably fast. Absolute efficiency/accuracy is often not needed.<br />
1585   An example, to have a <span class="term">rel</span> attribute with <span class="term">nofollow</span> for all links, and to disable links that do not point to domains <span class="term">abc.com</span> and <span class="term">xyz.org</span>:<br />
1588 <code class="code">    $config["anti_link_spam"] = array('`.`', '`://\W*(?!(abc\.com|xyz\.org))`');</code>
1592 <div class="sub-sub-section"><h4>
1593 <a name="s3.4.8" id="s3.4.8"></a><span class="item-no">3.4.8</span>  Inline style properties
1594 </h4><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1596   htmLawed can check URL schemes and dynamic expressions (to guard against Javascript, etc., script-based insecurities) in inline CSS style property values in the <span class="term">style</span> attributes. (CSS properties like <span class="term">background-image</span> that accept URLs in their values are noted in <a href="#s5.3">section 5.3</a>.) Dynamic CSS expressions that allow scripting in the IE browser, and can be a vulnerability, can be removed from property values by setting <span class="term">$config["css_expression"]</span> to <span class="term">1</span> (default setting). Note that when <span class="term">$config["css_expression"]</span> is set to <span class="term">1</span>, htmLawed will remove <span class="term">/*</span> from the <span class="term">style</span> values.<br />
1598   <strong>Note</strong>: Because of the various ways of representing characters in attribute values (URL-escapement, entitification, etc.), htmLawed might alter the values of the <span class="term">style</span> attribute values, and may even falsely identify dynamic CSS expressions and URL schemes in them. If this is an important issue, checking of URLs and dynamic expressions can be turned off (<span class="term">$config["schemes"] = "...style:*..."</span>, see <a href="#s3.4.3">section 3.4.3</a>, and <span class="term">$config["css_expression"] = 0</span>). Alternately, admins can use their own custom function for finer handling of <span class="term">style</span> values through the <span class="term">hook_tag</span> parameter (see <a href="#s3.4.9">section 3.4.9</a>).<br />
1600   It is also possible to have htmLawed let through any <span class="term">style</span> value by setting <span class="term">$config["style_pass"]</span> to <span class="term">1</span>.<br />
1602   As such, it is better to set up a CSS file with class declarations, disallow the <span class="term">style</span> attribute, set a <span class="term">$spec</span> rule (see <a href="#s2.3">section 2.3</a>) for <span class="term">class</span> for the <span class="term">oneof</span> or <span class="term">match</span> parameter, and ask writers to make use of the <span class="term">class</span> attribute.<br />
1605 <div class="sub-sub-section"><h4>
1606 <a name="s3.4.9" id="s3.4.9"></a><span class="item-no">3.4.9</span>  Hook function for tag content
1607 </h4><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1609   It is possible to utilize a custom hook function to alter the tag content htmLawed has finalized (i.e., after it has checked/corrected for required attributes, transformed attributes, lower-cased attribute names, etc.).<br />
1611   When <span class="term">$config</span> parameter <span class="term">hook_tag</span> is set to the name of a function, htmLawed (function <span class="term">hl_tag()</span>) will pass on the element name, and the <em>finalized</em> attribute name-value pairs as array elements to the function. The function, after completing a task such as filtering or tag transformation, will typically return an empty string, the full opening tag string like <span class="term"><element_name attribute_1_name="attribute_1_value"...></span> (for empty elements like <span class="term">img</span> and <span class="term">input</span>, the element-closing slash <span class="term">/</span> should also be included), etc.<br />
1613   Any <span class="term">hook_tag</span> function, since htmLawed version 1.1.11, also receives names of elements in closing tags, such as <span class="term">a</span> in the closing <span class="term"></a></span> tag of the element <span class="term"><a href="http://cnn.com">CNN</a></span>. No other value is passed to the function since a closing tag contains only element names. Typically, the function will return an empty string or a full closing tag (like <span class="term"></a></span>).<br />
1615   This is a <strong>powerful functionality</strong> that can be exploited for various objectives: consolidate-and-convert inline <span class="term">style</span> attributes to <span class="term">class</span>, convert <span class="term">embed</span> elements to <span class="term">object</span>, permit only one <span class="term">caption</span> element in a <span class="term">table</span> element, disallow embedding of certain types of media, <strong>inject HTML</strong>, use <a href="http://csstidy.sourceforge.net">CSSTidy</a> to sanitize <span class="term">style</span> attribute values, etc.<br />
1617   As an example, the custom hook code below can be used to force a series of specifically ordered <span class="term">id</span> attributes on all elements, and a specific <span class="term">param</span> element inside all <span class="term">object</span> elements:<br />
1620 <code class="code">    function my_tag_function($element, $attribute_array=0){</code>
1624 <code class="code">      // If second argument is not received, it means a closing tag is being handled</code>
1627 <code class="code">      if(is_numeric($attribute_array)){</code>
1630 <code class="code">        return "</$element>";</code>
1633 <code class="code">      }</code>
1637 <code class="code">      static $id = 0;</code>
1640 <code class="code">      // Remove any duplicate element</code>
1643 <code class="code">      if($element == 'param' && isset($attribute_array['allowscriptaccess'])){</code>
1646 <code class="code">        return '';</code>
1649 <code class="code">      }</code>
1653 <code class="code">      $new_element = '';</code>
1657 <code class="code">      // Force a serialized ID number</code>
1660 <code class="code">      $attribute_array['id'] = 'my_'. $id;</code>
1663 <code class="code">      ++$id;</code>
1667 <code class="code">      // Inject param for allowscriptaccess</code>
1670 <code class="code">      if($element == 'object'){</code>
1673 <code class="code">        $new_element = '<param id='my_'. $id; allowscriptaccess="never" />';</code>
1676 <code class="code">        ++$id;</code>
1679 <code class="code">      }</code>
1683 <code class="code">      $string = '';</code>
1686 <code class="code">      foreach($attribute_array as $k=>$v){</code>
1689 <code class="code">        $string .= " {$k}=\"{$v}\"";</code>
1692 <code class="code">      }</code>
1696 <code class="code">      static $empty_elements = array('area'=>1, 'br'=>1, 'col'=>1, 'command'=>1, 'embed'=>1, 'hr'=>1, 'img'=>1, 'input'=>1, 'isindex'=>1, 'keygen'=>1, 'link'=>1, 'meta'=>1, 'param'=>1, 'source'=>1, 'track'=>1, 'wbr'=>1);</code>
1700 <code class="code">      return "<{$element}{$string}". (array_key_exists($element, $empty_elements) ? ' /' : ''). '>'. $new_element;</code>
1703 <code class="code">    }</code>
1706   The <span class="term">hook_tag</span> parameter is different from the <span class="term">hook</span> parameter (<a href="#s3.7">section 3.7</a>).<br />
1708   Snippets of hook function code developed by others may be available on the <a href="http://www.bioinformatics.org/phplabware/internal_utilities/htmLawed">htmLawed</a> website.<br />
1711 <div class="sub-section"><h3>
1712 <a name="s3.5" id="s3.5"></a><span class="item-no">3.5</span>  Simple configuration directive for most valid XHTML
1713 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1715   If <span class="term">$config["valid_xhtml"]</span> is set to <span class="term">1</span>, some relevant <span class="term">$config</span> parameters (indicated by <span class="term">~</span> in <a href="#s2.2">section 2.2</a>) are auto-adjusted. This allows one to pass the <span class="term">$config</span> argument with a simpler value. If a value for a parameter auto-set through <span class="term">valid_xhtml</span> is still manually provided, then that value will over-ride the auto-set value.<br />
1718 <div class="sub-section"><h3>
1719 <a name="s3.6" id="s3.6"></a><span class="item-no">3.6</span>  Simple configuration directive for most <em>safe</em> HTML
1720 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1722   <em>Safe</em> HTML refers to HTML that is restricted to reduce the vulnerability for scripting attacks (such as XSS) based on HTML code which otherwise may still be legal and compliant with the HTML standard specifications. When elements such as <span class="term">script</span> and <span class="term">object</span>, and attributes such as <span class="term">onmouseover</span> and <span class="term">style</span> are allowed in the input text, an input writer can introduce malevolent HTML code. Note that what is considered <span class="term">safe</span> depends on the nature of the web application and the trust-level accorded to its users.<br />
1724   htmLawed allows an admin to use <span class="term">$config["safe"]</span> to auto-adjust multiple <span class="term">$config</span> parameters (such as <span class="term">elements</span> which declares the allowed element-set), which otherwise would have to be manually set. The relevant parameters are indicated by <span class="term">"</span> in <a href="#s2.2">section 2.2</a>). Thus, one can pass the <span class="term">$config</span> argument with a simpler value. Having the <span class="term">safe</span> parameter set to <span class="term">1</span> is equivalent to setting the following <span class="term">$config</span> parameters to the noted values :<br />
1727 <code class="code">    cdata - 0</code>
1730 <code class="code">    comment - 0</code>
1733 <code class="code">    deny_attribute - on*</code>
1736 <code class="code">    elements - * -applet -audio -canvas -embed -iframe -object -script -video</code>
1739 <code class="code">    schemes - href: aim, feed, file, ftp, gopher, http, https, irc, mailto, news, nntp, sftp, ssh, tel, telnet; style: !; *:file, http, https</code>
1742   With <span class="term">safe</span> set to <span class="term">1</span>, htmLawed considers <span class="term">CDATA</span> sections and HTML comments as plain text, and prohibits the <span class="term">applet</span>, <span class="term">audio</span>, <span class="term">canvas</span>, <span class="term">embed</span>, <span class="term">iframe</span>, <span class="term">object</span>, <span class="term">script</span> and <span class="term">video</span> elements, and the <span class="term">on*</span> attributes like <span class="term">onclick</span>. ( There are <span class="term">$config</span> parameters like <span class="term">css_expression</span> that are not affected by the value set for <span class="term">safe</span> but whose default values still contribute towards a more <em>safe</em> output.) Further, unless overridden by the value for parameter <span class="term">schemes</span> (see <a href="#s3.4.3">section 3.4.3</a>), the schemes <span class="term">app</span>, <span class="term">data</span> and <span class="term">javascript</span> are not permitted, and URLs with schemes are neutralized so that, e.g., <span class="term">style="moz-binding:url(http://danger)"</span> becomes <span class="term">style="moz-binding:url(denied:http://danger)"</span>.<br />
1744   Admins, however, may still want to completely deny the <span class="term">style</span> attribute, e.g., with code like<br />
1747 <code class="code">    $processed = htmLawed($text, array('safe'=>1, 'deny_attribute'=>'style'));</code>
1750   Permitting the <span class="term">style</span> attribute brings in risks of <em>click-jacking</em>, etc. CSS property values can render a page non-functional or be used to deface it. Except for URLs, dynamic expressions, and some other things, htmLawed does not completely check <span class="term">style</span> values. It does provide ways for the code-developer implementing htmLawed to do such checks through the <span class="term">$spec</span> argument, and through the <span class="term">hook_tag</span> parameter (see <a href="#s3.4.8">section 3.4.8</a> for more). Disallowing style completely and relying on CSS classes and stylesheet files is recommended.<br />
1752   If a value for a parameter auto-set through <span class="term">safe</span> is still manually provided, then that value can over-ride the auto-set value. E.g., with <span class="term">$config["safe"] = 1</span> and <span class="term">$config["elements"] = "* +script"</span>, <span class="term">script</span>, but not <span class="term">applet</span>, is allowed. Such over-ride does not occur for <span class="term">deny_attribute</span> (for legacy reason) when comma-separated attribute names are provided as the value for this parameter (<a href="#s3.4">section 3.4</a>); instead htmLawed will add <span class="term">on*</span> to the value provided for <span class="term">deny_attribute</span>.<br />
1754   A page illustrating the efficacy of htmLawed's anti-XSS abilities with <span class="term">safe</span> set to <span class="term">1</span> against XSS vectors listed by <a href="http://ha.ckers.org/xss.html">RSnake</a> may be available <a href="http://www.bioinformatics.org/phplabware/internal_utilities/htmLawed/rsnake/RSnakeXSSTest.htm">here</a>.<br />
1757 <div class="sub-section"><h3>
1758 <a name="s3.7" id="s3.7"></a><span class="item-no">3.7</span>  Using a hook function
1759 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1761   If <span class="term">$config["hook"]</span> is not set to <span class="term">0</span>, then htmLawed will allow preliminarily processed input to be altered by a hook function named by <span class="term">$config["hook"]</span> before starting the main work (but after handling of characters, entities, HTML comments and <span class="term">CDATA</span> sections -- see code for function <span class="term">htmLawed()</span>).<br />
1763   The hook function also allows one to alter the <em>finalized</em> values of <span class="term">$config</span> and <span class="term">$spec</span>.<br />
1765   Note that the <span class="term">hook</span> parameter is different from the <span class="term">hook_tag</span> parameter (<a href="#s3.4.9">section 3.4.9</a>).<br />
1767   Snippets of hook function code developed by others may be available on the <a href="http://www.bioinformatics.org/phplabware/internal_utilities/htmLawed">htmLawed</a> website.<br />
1770 <div class="sub-section"><h3>
1771 <a name="s3.8" id="s3.8"></a><span class="item-no">3.8</span>  Obtaining <em>finalized</em> parameter values
1772 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1774   htmLawed can assign the <em>finalized</em> <span class="term">$config</span> and <span class="term">$spec</span> values to a variable named by <span class="term">$config["show_setting"]</span>. The variable, made global by htmLawed, is set as an array with three keys: <span class="term">config</span>, with the <span class="term">$config</span> value, <span class="term">spec</span>, with the <span class="term">$spec</span> value, and <span class="term">time</span>, with a value that is the Unix time (the output of PHP's <span class="term">microtime()</span> function) when the value was assigned. Admins should use a PHP-compliant variable name (e.g., one that does not begin with a numerical digit) that does not conflict with variable names in their non-htmLawed code.<br />
1776   The values, which are also post-hook function (if any), can be used to auto-generate information (on, e.g., the elements that are permitted) for input writers.<br />
1779 <div class="sub-section"><h3>
1780 <a name="s3.9" id="s3.9"></a><span class="item-no">3.9</span>  Retaining non-HTML tags in input with mixed markup
1781 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1783   htmLawed does not remove certain characters that, though invalid, are nevertheless <em>discouraged</em> in HTML documents as per the specifications (see <a href="#s5.1">section 5.1</a>). This can be utilized to deal with input that contains mixed markup. Input that may have HTML markup as well as some other markup that is based on the <span class="term"><</span>, <span class="term">></span> and <span class="term">&</span> characters is considered to have mixed markup. The non-HTML markup can be rather proprietary (like markup for emoticons/smileys), or standard (like MathML or SVG). Or it can be programming code meant for execution/evaluation (such as embedded PHP code).<br />
1785   To deal with such mixed markup, the input text can be pre-processed to hide the non-HTML markup by specifically replacing the <span class="term"><</span>, <span class="term">></span> and <span class="term">&</span> characters with some of the HTML-discouraged characters (see <a href="#s3.1.2">section 3.1.2</a>). Post-htmLawed processing, the replacements are reverted.<br />
1787   An example (mixed HTML and PHP code in input text):<br />
1790 <code class="code">    $text = preg_replace('`<\?php(.+?)\?>`sm', "\x83?php\\1?\x84", $text);</code>
1793 <code class="code">    $processed = htmLawed($text);</code>
1796 <code class="code">    $processed = preg_replace('`\x83\?php(.+?)\?\x84`sm', '<?php$1?>', $processed);</code>
1799   This code will not work if <span class="term">$config["clean_ms_char"]</span> is set to <span class="term">1</span> (<a href="#s3.1">section 3.1</a>), in which case one should instead deploy a hook function (<a href="#s3.7">section 3.7</a>). (htmLawed internally uses certain control characters, code-points <span class="term">1</span> to <span class="term">7</span>, and use of these characters as markers in the logic of hook functions may cause issues.)<br />
1801   Admins may also be able to use <span class="term">$config["and_mark"]</span> to deal with such mixed markup; see <a href="#s3.2">section 3.2</a>.<br />
1805 <div class="section"><h2>
1806 <a name="s4" id="s4"></a><span class="item-no">4</span>  Other
1807 </h2><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1808 <div class="sub-section"><h3>
1809 <a name="s4.1" id="s4.1"></a><span class="item-no">4.1</span>  Support
1810 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1812   Software updates and forum-based community-support may be found at <a href="http://www.bioinformatics.org/phplabware/internal_utilities/htmLawed">http://www.bioinformatics.org/phplabware/internal_utilities/htmLawed</a>. For general PHP issues (not htmLawed-specific), support may be found through internet searches and at <a href="http://php.net">http://php.net</a>.<br />
1815 <div class="sub-section"><h3>
1816 <a name="s4.2" id="s4.2"></a><span class="item-no">4.2</span>  Known issues
1817 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1819   See <a href="#s2.8">section 2.8</a>.<br />
1822 <div class="sub-section"><h3>
1823 <a name="s4.3" id="s4.3"></a><span class="item-no">4.3</span>  Change-log
1824 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1826   (The release date for the downloadable package of files containing documentation, demo script, test-cases, etc., besides the <span class="term">htmLawed.php</span> file, may be updated without a change-log entry if the secondary files, but not htmLawed per se, are revised.)<br />
1828   <em>Version number - Release date. Notes</em><br />
1830   1.2.4.1 - 12 September 2017. Corrects a function re-declaration bug introduced in version 1.2.4<br />
1832   1.2.4 - 31 August 2017. Removes use of PHP <span class="term">create_function</span> function and <span class="term">$php_errormsg</span> reserved variable (deprecated in PHP 7.2)<br />
1834   1.2.3 - 5 July 2017. New option value of <span class="term">4</span> for <span class="term">$config["comments"]</span> to stop enforcing a space character before the <span class="term">--></span> comment-closing marker<br />
1836   1.2.2 - 25 May 2017. Fix for a bug in parsing <span class="term">$spec</span> that got introduced in version 1.2; also, <span class="term">$spec</span> is now parsed to accommodate specifications for an HTML element when they are specified in multiple rules<br />
1838   1.2.1.1 - 17 May 2017. Fix for a potential security vulnerability in transformation of deprecated attributes<br />
1840   1.2.1 - 15 May 2017. Fix for a potential security vulnerability in transformation of deprecated attributes<br />
1842   1.2 - 11 February 2017. (First beta release on 26 May 2013). Added support for HTML version 5; ARIA, data-* and microdata attributes; <span class="term">app</span>, <span class="term">data</span>, <span class="term">javascript</span> and <span class="term">tel</span> URL schemes (thus, <span class="term">javascript:</span> is not filtered in default mode). Removed support for code using Kses functions (see <a href="#s2.6">section 2.6</a>). Changes in revisions to the beta releases are not noted here.<br />
1844   1.1.22 - 5 March 2016. Improved testing of attribute value rules specified in <span class="term">$spec</span><br />
1846   1.1.21 - 27 February 2016. Improvement and security fix in transforming <span class="term">font</span> element<br />
1848   1.1.20 - 9 June 2015. Fix for a potential security vulnerability arising from unescaped double-quote character in single-quoted attribute value of some deprecated elements when tag transformation is enabled; recognition for non-(HTML 4) standard <span class="term">allowfullscreen</span> attribute of <span class="term">iframe</span><br />
1850   1.1.19 - 19 January 2015. Fix for a bug in cleaning of soft-hyphens in URL values, etc<br />
1852   1.1.18 - 2 August 2014. Fix for a potential security vulnerability arising from specially encoded text with serial opening tags<br />
1854   1.1.17 - 11 March 2014. Removed use of PHP function preg_replace with <span class="term">e</span> modifier for compatibility with PHP 5.5.<br />
1856   1.1.16 - 29 August 2013. Fix for a potential security vulnerability arising from specialy encoded space characters in URL schemes/protocols<br />
1858   1.1.15 - 11 August 2013. Improved tidying/prettifying functionality<br />
1860   1.1.14 - 8 August 2012. Fix for possible segmental loss of incremental indentation during <span class="term">tidying</span> when <span class="term">balance</span> is disabled; fix for non-effectuation under some circumstances of a corrective behavior to preserve plain text within elements like <span class="term">blockquote</span><br />
1862   1.1.13 - 22 July 2012. Added feature allowing use of custom, non-standard attributes or custom rules for standard attributes<br />
1864   1.1.12 - 5 July 2012. Fix for a bug in identifying an unquoted value of the <span class="term">face</span> attribute<br />
1866   1.1.11 - 5 June 2012. Fix for possible problem with handling of multi-byte characters in attribute values in an mbstring.func_overload enviroment. <span class="term">$config["hook_tag"]</span>, if specified, now receives names of elements in closing tags.<br />
1868   1.1.10 - 22 October 2011. Fix for a bug in the <span class="term">tidy</span> functionality that caused the entire input to be replaced with a single space; new parameter, <span class="term">$config["direct_list_nest"]</span> to allow direct descendance of a list in a list. (5 April 2012. Dual licensing from LGPLv3 to LGPLv3 and GPLv2+.)<br />
1870   1.1.9.5 - 6 July 2011. Minor correction of a rule for nesting of <span class="term">li</span> within <span class="term">dir</span><br />
1872   1.1.9.4 - 3 July 2010. Parameter <span class="term">schemes</span> now accepts <span class="term">!</span> so any URL, even a local one, can be <em>denied</em>. An issue in which a second URL value in <span class="term">style</span> properties was not checked was fixed.<br />
1874   1.1.9.3 - 17 May 2010. Checks for correct nesting of <span class="term">param</span><br />
1876   1.1.9.2 - 26 April 2010. Minor fix regarding rendering of denied URL schemes<br />
1878   1.1.9.1 - 26 February 2010. htmLawed now uses the LGPL version 3 license; support for <span class="term">flashvars</span> attribute for <span class="term">embed</span><br />
1880   1.1.9 - 22 December 2009. Soft-hyphens are now removed only from URL-accepting attribute values<br />
1882   1.1.8.1 - 16 July 2009. Minor code-change to fix a PHP error notice<br />
1884   1.1.8 - 23 April 2009. Parameter <span class="term">deny_attribute</span> now accepts the wild-card <span class="term">*</span>, making it simpler to specify its value when all but a few attributes are being denied; fixed a bug in interpreting <span class="term">$spec</span><br />
1886   1.1.7 - 11-12 March 2009. Attributes globally denied through <span class="term">deny_attribute</span> can be allowed element-specifically through <span class="term">$spec</span>; <span class="term">$config["style_pass"]</span> allowing letting through any <span class="term">style</span> value introduced; altered logic to catch certain types of dynamic crafted CSS expressions<br />
1888   1.1.3-6 - 28-31 January - 4 February 2009. Altered logic to catch certain types of dynamic crafted CSS expressions<br />
1890   1.1.2 - 22 January 2009. Fixed bug in parsing of <span class="term">font</span> attributes during tag transformation<br />
1892   1.1.1 - 27 September 2008. Better nesting correction when omitable closing tags are absent<br />
1894   1.1 - 29 June 2008. <span class="term">$config["hook_tag"]</span> and <span class="term">$config["tidy"]</span> introduced for custom tag/attribute check/modification/injection and output compaction/beautification; fixed a regex-in-$spec parsing bug<br />
1896   1.0.9 - 11 June 2008. Fix for a bug in checks for invalid HTML code-point entities<br />
1898   1.0.8 - 15 May 2008. Permit <span class="term">bordercolor</span> attribute for <span class="term">table</span>, <span class="term">td</span> and <span class="term">tr</span><br />
1900   1.0.7 - 1 May 2008. Support for <span class="term">wmode</span> attribute for <span class="term">embed</span>; <span class="term">$config["show_setting"]</span> introduced; improved <span class="term">$config["elements"]</span> evaluation<br />
1902   1.0.6 - 20 April 2008. <span class="term">$config["and_mark"]</span> introduced<br />
1904   1.0.5 - 12 March 2008. <span class="term">style</span> URL schemes essentially disallowed when $config <span class="term">safe</span> is on; improved regex for CSS expression search<br />
1906   1.0.4 - 10 March 2008. Improved corrections for <span class="term">blockquote</span>, <span class="term">form</span>, <span class="term">map</span> and <span class="term">noscript</span><br />
1908   1.0.3 - 3 March 2008. Character entities for soft-hyphens are now replaced with spaces (instead of being removed); fix for a bug allowing <span class="term">td</span> directly inside <span class="term">table</span>; <span class="term">$config["safe"]</span> introduced<br />
1910   1.0.2 - 13 February 2008. Improved implementation of <span class="term">$config["keep_bad"]</span><br />
1912   1.0.1 - 7 November 2007. Improved regex for identifying URLs, protocols and dynamic expressions (<span class="term">hl_tag()</span> and <span class="term">hl_prot()</span>); no error display with <span class="term">hl_regex()</span><br />
1914   1.0 - 2 November 2007. First release<br />
1917 <div class="sub-section"><h3>
1918 <a name="s4.4" id="s4.4"></a><span class="item-no">4.4</span>  Testing
1919 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1921   To test htmLawed using a form interface, a <a href="htmLawedTest.php">demo</a> web-page is provided with the htmLawed distribution (<span class="term">htmLawed.php</span> and <span class="term">htmLawedTest.php</span> should be in the same directory on the web-server). A file with <a href="htmLawed_TESTCASE.txt">test-cases</a> is also provided.<br />
1924 <div class="sub-section"><h3>
1925 <a name="s4.5" id="s4.5"></a><span class="item-no">4.5</span>  Upgrade, & old versions
1926 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1928   Upgrading is as simple as replacing the previous version of <span class="term">htmLawed.php</span>, assuming the file was not modified for customized features. As htmLawed output is almost always used in static documents, upgrading should not affect old, finalized content.<br />
1930   <strong>Note:</strong> The following upgrades may affect the functionality of a specific htmLawed installation:<br />
1932   (1) From version 1.1-1.1.10 to 1.1.11 or later, if a <span class="term">hook_tag</span> function is in use: In version 1.1.11 and later, elements in closing tags (and not just the opening tags) are also passed to the function. There are no attribute names/values to pass, so a <span class="term">hook_tag</span> function receives only the element name. The <span class="term">hook_tag</span> function therefore may have to be edited. See <a href="#s3.4.9">section 3.4.9</a>.<br />
1934   (2) From version older than 1.2.beta to later, if htmLawed was used as Kses replacement with Kses code in use: In version 1.2.beta or later, htmLawed no longer provides direct support for code that uses Kses functions (see <a href="#s2.6">section 2.6</a>).<br />
1936   (3) From version older than 1.2 to later, if htmLawed is used without <span class="term">$config["safe"]</span> set to 1: Unlike previous versions, htmLawed version 1.2 and later permit <span class="term">data</span> and <span class="term">javascript</span> URL schemes by default (see <a href="#s3.4.3">section 3.4.3</a>).<br />
1938   Old versions of htmLawed may be available online. E.g., for version 1.0, check <a href="http://www.bioinformatics.org/phplabware/downloads/htmLawed1.zip">http://www.bioinformatics.org/phplabware/downloads/htmLawed1.zip</a>; for 1.1.1, <a href="http://www.bioinformatics.org/phplabware/downloads/htmLawed111.zip">http://www.bioinformatics.org/phplabware/downloads/htmLawed111.zip</a>; and for 1.1.22, <a href="http://www.bioinformatics.org/phplabware/downloads/htmLawed1122.zip">http://www.bioinformatics.org/phplabware/downloads/htmLawed1122.zip</a>.<br />
1941 <div class="sub-section"><h3>
1942 <a name="s4.6" id="s4.6"></a><span class="item-no">4.6</span>  Comparison with <span class="term">HTMLPurifier</span>
1943 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1945   The HTMLPurifier PHP library by Edward Yang is a very good HTML filtering script that uses object oriented PHP code. Compared to htmLawed, it (as of year 2015):<br />
1947   *  does not support PHP versions older than 5.0 (HTMLPurifier dropped PHP 4 support after version 2)<br />
1949   *  is 15-20 times bigger (scores of files totalling more than 750 kb)<br />
1951   *  consumes 10-15 times more RAM memory (just including the HTMLPurifier files without calling the filter requires a few MBs of memory)<br />
1953   *  is expectedly slower<br />
1955   *  lacks many of the extra features of htmLawed (like entity conversions and code compaction/beautification)<br />
1957   *  has poor documentation<br />
1959   However, HTMLPurifier has finer checks for character encodings and attribute values, and can log warnings and errors. Visit the HTMLPurifier <a href="http://htmlpurifier.org">website</a> for updated information.<br />
1962 <div class="sub-section"><h3>
1963 <a name="s4.7" id="s4.7"></a><span class="item-no">4.7</span>  Use through application plug-ins/modules
1964 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1966   Plug-ins/modules to implement htmLawed in applications such as Drupal may have been developed. Check the application websites and the htmLawed <a href="http://www.bioinformatics.org/phplabware/internal_utilities/htmLawed">forum</a>.<br />
1969 <div class="sub-section"><h3>
1970 <a name="s4.8" id="s4.8"></a><span class="item-no">4.8</span>  Use in non-PHP applications
1971 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1973   Non-PHP applications written in Python, Ruby, etc., may be able to use htmLawed through system calls to the PHP engine. Such code may have been documented on the internet. Also check the forum on the htmLawed <a href="http://www.bioinformatics.org/phplabware/internal_utilities/htmLawed">site</a>.<br />
1976 <div class="sub-section"><h3>
1977 <a name="s4.9" id="s4.9"></a><span class="item-no">4.9</span>  Donate
1978 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1980   A donation in any currency and amount to appreciate or support this software can be sent by <a href="http://paypal.com">PayPal</a> to this email address: drpatnaik at yahoo dot com.<br />
1983 <div class="sub-section"><h3>
1984 <a name="s4.10" id="s4.10"></a><span class="item-no">4.10</span>  Acknowledgements
1985 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1987   Nicholas Alipaz, Bryan Blakey, Pádraic Brady, Dac Chartrand, Alexandre Chouinard, Ulf Harnhammer, Gareth Heyes, Hakre, Klaus Leithoff, Lukasz Pilorz, Shelley Powers, Psych0tr1a, Lincoln Russell, Tomas Sykorka, Harro Verton, Edward Yang, and many anonymous users.<br />
1989   Thank you!<br />
1993 <div class="section"><h2>
1994 <a name="s5" id="s5"></a><span class="item-no">5</span>  Appendices
1995 </h2><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
1996 <div class="sub-section"><h3>
1997 <a name="s5.1" id="s5.1"></a><span class="item-no">5.1</span>  Characters discouraged in XHTML
1998 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
2000   Characters represented by the following hexadecimal code-points are <em>not</em> invalid, even though some validators may issue messages stating otherwise.<br />
2002   <span class="term">7f</span> to <span class="term">84</span>, <span class="term">86</span> to <span class="term">9f</span>, <span class="term">fdd0</span> to <span class="term">fddf</span>, <span class="term">1fffe</span>, <span class="term">1ffff</span>, <span class="term">2fffe</span>, <span class="term">2ffff</span>, <span class="term">3fffe</span>, <span class="term">3ffff</span>, <span class="term">4fffe</span>, <span class="term">4ffff</span>, <span class="term">5fffe</span>, <span class="term">5ffff</span>, <span class="term">6fffe</span>, <span class="term">6ffff</span>, <span class="term">7fffe</span>, <span class="term">7ffff</span>, <span class="term">8fffe</span>, <span class="term">8ffff</span>, <span class="term">9fffe</span>, <span class="term">9ffff</span>, <span class="term">afffe</span>, <span class="term">affff</span>, <span class="term">bfffe</span>, <span class="term">bffff</span>, <span class="term">cfffe</span>, <span class="term">cffff</span>, <span class="term">dfffe</span>, <span class="term">dffff</span>, <span class="term">efffe</span>, <span class="term">effff</span>, <span class="term">ffffe</span>, <span class="term">fffff</span>, <span class="term">10fffe</span> and <span class="term">10ffff</span><br />
2005 <div class="sub-section"><h3>
2006 <a name="s5.2" id="s5.2"></a><span class="item-no">5.2</span>  Valid attribute-element combinations
2007 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
2009   *  includes deprecated attributes (marked <span class="term">^</span>), attributes for microdata (marked <span class="term">*</span>), the non-standard <span class="term">bordercolor</span>, and new-in-HTML5 attributes (marked <span class="term">~</span>); can have multiple comma-separated values (marked <span class="term">%</span>); can have multiple space-separated values (marked <span class="term">$</span>)<br />
2010   *  only non-frameset, HTML body elements<br />
2011   *  <span class="term">name</span> for <span class="term">a</span> and <span class="term">map</span>, and <span class="term">lang</span> are invalid in XHTML 1.1<br />
2012   *  <span class="term">target</span> is valid for <span class="term">a</span> in XHTML 1.1 and higher<br />
2013   *  <span class="term">xml:space</span> is only for XHTML 1.1<br />
2015   abbr - td, th<br />
2016   accept - form, input<br />
2017   accept-charset - form<br />
2018   action - form<br />
2019   align - applet, caption^, col, colgroup, div^, embed, h1^, h2^, h3^, h4^, h5^, h6^, hr^, iframe, img^, input^, legend^, object^, p^, table^, tbody, td, tfoot, th, thead, tr<br />
2020   allowfullscreen - iframe<br />
2021   alt - applet, area, img, input<br />
2022   archive - applet, object<br />
2023   async~ - script<br />
2024   autocomplete~ - input<br />
2025   autofocus~ - button, input, keygen, select, textarea<br />
2026   autoplay~ - audio, video<br />
2027   axis - td, th<br />
2028   bgcolor - embed, table^, td^, th^, tr^<br />
2029   border - img, object^, table<br />
2030   bordercolor - table, td, tr<br />
2031   cellpadding - table<br />
2032   cellspacing - table<br />
2033   challenge~ - keygen<br />
2034   char - col, colgroup, tbody, td, tfoot, th, thead, tr<br />
2035   charoff - col, colgroup, tbody, td, tfoot, th, thead, tr<br />
2036   charset - a, script<br />
2037   checked - command, input<br />
2038   cite - blockquote, del, ins, q<br />
2039   classid - object<br />
2040   clear - br^<br />
2041   code - applet<br />
2042   codebase - object, applet<br />
2043   codetype - object<br />
2044   color - font<br />
2045   cols - textarea<br />
2046   colspan - td, th<br />
2047   compact - dir, dl^, menu, ol^, ul^<br />
2048   content - meta<br />
2049   controls~ - audio, video<br />
2050   coords - area, a<br />
2051   crossorigin~ - img<br />
2052   data - object<br />
2053   datetime - del, ins, time<br />
2054   declare - object<br />
2055   default~ - track<br />
2056   defer - script<br />
2057   dir - bdo<br />
2058   dirname~ - input, textarea<br />
2059   disabled - button, command, fieldset, input, keygen, optgroup, option, select, textarea<br />
2060   download~ - a<br />
2061   enctype - form<br />
2062   face - font<br />
2063   flashvars** - embed<br />
2064   for - label, output<br />
2065   form~ - button, fieldset, input, keygen, label, object, output, select, textarea<br />
2066   formaction~ - button, input<br />
2067   formenctype~ - button, input<br />
2068   formmethod~ - button, input<br />
2069   formnovalidate~ - button, input<br />
2070   formtarget~ - button, input<br />
2071   frame - table<br />
2072   frameborder - iframe<br />
2073   headers - td, th<br />
2074   height - applet, canvas, embed, iframe, img, input, object, td^, th^, video<br />
2075   high~ - meter<br />
2076   href - a, area, link<br />
2077   hreflang - a, area, link<br />
2078   hspace - applet, embed, img^, object^<br />
2079   icon~ - command<br />
2080   ismap - img, input<br />
2081   keytype~ - keygen<br />
2082   keyparams~ - keygen<br />
2083   kind~ - track<br />
2084   label - command, menu, option, optgroup, track<br />
2085   language - script^<br />
2086   list~ - input<br />
2087   longdesc - img, iframe<br />
2088   loop~ - audio, video<br />
2089   low~ - meter<br />
2090   marginheight - iframe<br />
2091   marginwidth - iframe<br />
2092   max~ - input, meter, progress<br />
2093   maxlength - input, textarea<br />
2094   media~ - a, area, link, source, style<br />
2095   mediagroup~ - audio, video<br />
2096   method - form<br />
2097   min~ - input, meter<br />
2098   model** - embed<br />
2099   multiple - input, select<br />
2100   muted~ - audio, video<br />
2101   name - a^, applet^, button, embed, fieldset, form^, iframe^, img^, input, keygen, map^, object, output, param, select, textarea<br />
2102   nohref - area<br />
2103   noshade - hr^<br />
2104   novalidate~ - form<br />
2105   nowrap - td^, th^<br />
2106   object - applet<br />
2107   open~ - details<br />
2108   optimum~ - meter<br />
2109   pattern~ - input<br />
2110   ping~ - a, area<br />
2111   placeholder~ - input, textarea<br />
2112   pluginspage** - embed<br />
2113   pluginurl** - embed<br />
2114   poster~ - video<br />
2115   pqg~ - keygen<br />
2116   preload~ - audio, video<br />
2117   prompt - isindex<br />
2118   pubdate~ - time<br />
2119   radiogroup* - command<br />
2120   readonly - input, textarea<br />
2121   required~ - input, select, textarea<br />
2122   rel$ - a, area, link<br />
2123   rev - a<br />
2124   reversed~ - old<br />
2125   rows - textarea<br />
2126   rowspan - td, th<br />
2127   rules - table<br />
2128   sandbox~ - iframe<br />
2129   scope - td, th<br />
2130   scoped~ - style<br />
2131   scrolling - iframe<br />
2132   seamless~ - iframe<br />
2133   selected - option<br />
2134   shape - area, a<br />
2135   size - font, hr^, input, select<br />
2136   sizes~ - link<br />
2137   span - col, colgroup<br />
2138   src - audio, embed, iframe, img, input, script, source, track, video<br />
2139   srcdoc~ - iframe<br />
2140   srclang~ - track<br />
2141   srcset~% - img<br />
2142   standby - object<br />
2143   start - ol<br />
2144   step~ - input<br />
2145   summary - table<br />
2146   target - a, area, form<br />
2147   type - a, area, button, command, embed, input, li, link, menu, object, ol, param, script, source, style, ul<br />
2148   typemustmatch~ - object<br />
2149   usemap - img, input, object<br />
2150   valign - col, colgroup, tbody, td, tfoot, th, thead, tr<br />
2151   value - button, data, input, li, meter, option, param, progress<br />
2152   valuetype - param<br />
2153   vspace - applet, embed, img^, object^<br />
2154   width - applet, canvas, col, colgroup, embed, hr^, iframe, img, input, object, pre^, table, td^, th^, video<br />
2155   wmode - embed<br />
2156   wrap~ - textarea<br />
2158   The following attributes, including event-specific ones and attributes of ARIA and microdata specifications, are considered global and allowed in all elements:<br />
2160   accesskey, aria-activedescendant, aria-atomic, aria-autocomplete, aria-busy, aria-checked, aria-controls, aria-describedby, aria-disabled, aria-dropeffect, aria-expanded, aria-flowto, aria-grabbed, aria-haspopup, aria-hidden, aria-invalid, aria-label, aria-labelledby, aria-level, aria-live, aria-multiline, aria-multiselectable, aria-orientation, aria-owns, aria-posinset, aria-pressed, aria-readonly, aria-relevant, aria-required, aria-selected, aria-setsize, aria-sort, aria-valuemax, aria-valuemin, aria-valuenow, aria-valuetext, class$, contenteditable, contextmenu, dir, draggable, dropzone, hidden, id, inert, itemid, itemprop, itemref, itemscope, itemtype, lang, onabort, onblur, oncanplay, oncanplaythrough, onchange, onclick, oncontextmenu, oncopy, oncuechange, oncut, ondblclick, ondrag, ondragend, ondragenter, ondragleave, ondragover, ondragstart, ondrop, ondurationchange, onemptied, onended, onerror, onfocus, onformchange, onforminput, oninput, oninvalid, onkeydown, onkeypress, onkeyup, onload, onloadeddata, onloadedmetadata, onloadstart, onlostpointercapture, onmousedown, onmousemove, onmouseout, onmouseover, onmouseup, onmousewheel, onpaste, onpause, onplay, onplaying, onpointercancel, ongotpointercapture, onpointerdown, onpointerenter, onpointerleave, onpointermove, onpointerout, onpointerover, onpointerup, onprogress, onratechange, onreadystatechange, onreset, onsearch, onscroll, onseeked, onseeking, onselect, onshow, onstalled, onsubmit, onsuspend, ontimeupdate, ontoggle, ontouchcancel, ontouchend, ontouchmove, ontouchstart, onvolumechange, onwaiting, onwheel, role, spellcheck, style, tabindex, title, translate, xmlns, xml:base, xml:lang, xml:space<br />
2162   Custom <em>data-*</em> attributes, where the first three characters of the value of <em>star</em> (*) after lower-casing do not equal <span class="term">xml</span> and the value of <em>star</em> does not have a colon (:), equal-to (=), newline, solidus (/), space, tab, or any A-Z character, are also considered global and allowed in all elements.<br />
2165 <div class="sub-section"><h3>
2166 <a name="s5.3" id="s5.3"></a><span class="item-no">5.3</span>  CSS 2.1 properties accepting URLs
2167 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
2169   background<br />
2170   background-image<br />
2171   content<br />
2172   cue-after<br />
2173   cue-before<br />
2175   list-style<br />
2176   list-style-image<br />
2177   play-during<br />
2180 <div class="sub-section"><h3>
2181 <a name="s5.4" id="s5.4"></a><span class="item-no">5.4</span>  Microsoft Windows 1252 character replacements
2182 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
2184   Key: <span class="term">d</span> double, <span class="term">l</span> left, <span class="term">q</span> quote, <span class="term">r</span> right, <span class="term">s.</span> single<br />
2186   Code-point (decimal) - hexadecimal value - replacement entity - represented character<br />
2188   127 - 7f - (removed) - (not used)<br />
2189   128 - 80 - &#8364; - euro<br />
2190   129 - 81 - (removed) - (not used)<br />
2191   130 - 82 - &#8218; - baseline s. q<br />
2192   131 - 83 - &#402; - florin<br />
2193   132 - 84 - &#8222; - baseline d q<br />
2194   133 - 85 - &#8230; - ellipsis<br />
2195   134 - 86 - &#8224; - dagger<br />
2196   135 - 87 - &#8225; - d dagger<br />
2197   136 - 88 - &#710; - circumflex accent<br />
2198   137 - 89 - &#8240; - permile<br />
2199   138 - 8a - &#352; - S Hacek<br />
2200   139 - 8b - &#8249; - l s. guillemet<br />
2201   140 - 8c - &#338; - OE ligature<br />
2202   141 - 8d - (removed) - (not used)<br />
2203   142 - 8e - &#381; - Z dieresis<br />
2204   143 - 8f - (removed) - (not used)<br />
2205   144 - 90 - (removed) - (not used)<br />
2206   145 - 91 - &#8216; - l s. q<br />
2207   146 - 92 - &#8217; - r s. q<br />
2208   147 - 93 - &#8220; - l d q<br />
2209   148 - 94 - &#8221; - r d q<br />
2210   149 - 95 - &#8226; - bullet<br />
2211   150 - 96 - &#8211; - en dash<br />
2212   151 - 97 - &#8212; - em dash<br />
2213   152 - 98 - &#732; - tilde accent<br />
2214   153 - 99 - &#8482; - trademark<br />
2215   154 - 9a - &#353; - s Hacek<br />
2216   155 - 9b - &#8250; - r s. guillemet<br />
2217   156 - 9c - &#339; - oe ligature<br />
2218   157 - 9d - (removed) - (not used)<br />
2219   158 - 9e - &#382; - z dieresis<br />
2220   159 - 9f - &#376; - Y dieresis<br />
2223 <div class="sub-section"><h3>
2224 <a name="s5.5" id="s5.5"></a><span class="item-no">5.5</span>  URL format
2225 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
2227   An <em>absolute</em> URL has a <span class="term">protocol</span> or <span class="term">scheme</span>, a <span class="term">network location</span> or <span class="term">hostname</span>, and, optional <span class="term">path</span>, <span class="term">parameters</span>, <span class="term">query</span> and <span class="term">fragment</span> segments. Thus, an absolute URL has this generic structure:<br />
2230 <code class="code">    (scheme) : (//network location) /(path) ;(parameters) ?(query) #(fragment)</code>
2233   The schemes can only contain letters, digits, <span class="term">+</span>, <span class="term">.</span> and <span class="term">-</span>. Hostname is the portion after the <span class="term">//</span> and up to the first <span class="term">/</span> (if any; else, up to the end) when <span class="term">:</span> is followed by a <span class="term">//</span> (e.g., <span class="term">abc.com</span> in <span class="term">ftp://abc.com/def</span>); otherwise, it consists of everything after the <span class="term">:</span> (e.g., <span class="term">def@abc.com</span> in mailto:def@abc.com').<br />
2235   <em>Relative</em> URLs do not have explicit schemes and network locations; such values are inherited from a <em>base</em> URL.<br />
2238 <div class="sub-section"><h3>
2239 <a name="s5.6" id="s5.6"></a><span class="item-no">5.6</span>  Brief on htmLawed code
2240 </h3><span class="totop"><a href="#peak">(to top)</a></span><br style="clear: both;" />
2242   Much of the code's logic and reasoning can be understood from the documentation above.<br />
2244   The <strong>output</strong> of htmLawed is a text string containing the processed input. There is no custom error tracking.<br />
2246   <strong>Function arguments</strong> for htmLawed are:<br />
2248   *  <span class="term">$in</span> - first argument; a text string; the <strong>input text</strong> to be processed. Any extraneous slashes added by PHP when <em>magic quotes</em> are enabled should be removed beforehand using PHP's <span class="term">stripslashes()</span> function.<br />
2250   *  <span class="term">$config</span> - second argument; an associative array; optional; named <span class="term">$C</span> within htmLawed code. The array has keys with names like <span class="term">balance</span> and <span class="term">keep_bad</span>, and the values, which can be boolean, string, or array, depending on the key, are read to accordingly set the <strong>configurable parameters</strong> (indicated by the keys). All configurable parameters receive some default value if the value to be used is not specified by the user through <span class="term">$config</span>. <em>Finalized</em> <span class="term">$config</span> is thus a filtered and possibly larger array.<br />
2252   *  <span class="term">$spec</span> - third argument; a text string; optional. The string has rules, written in an htmLawed-designated format, <strong>specifying</strong> element-specific attribute and attribute value restrictions. Function <span class="term">hl_spec()</span> is used to convert the string to an associative-array, named <span class="term">$S</span> within htmLawed code, for internal use. <em>Finalized</em> <span class="term">$spec</span> is thus an array.<br />
2254   <em>Finalized</em> <span class="term">$config</span> and <span class="term">$spec</span> are made <strong>global variables</strong> while htmLawed is at work. Values of any pre-existing global variables with same names are noted, and their values are restored after htmLawed finishes processing the input (to capture the <em>finalized</em> values, the <span class="term">show_settings</span> parameter of <span class="term">$config</span> should be used). Depending on <span class="term">$config</span>, another global variable <span class="term">hl_Ids</span>, to track <span class="term">id</span> attribute values for uniqueness, may be set. Unlike the other two variables, this one is not reset (or unset) post-processing.<br />
2256   Except for the main <span class="term">htmLawed()</span> function, htmLawed's functions are <strong>name-spaced</strong> using the <span class="term">hl_</span> prefix. The <strong>functions</strong> and their roles are:<br />
2258   *  <span class="term">hl_attrval</span> - check attribute values against <span class="term">$spec</span><br />
2259   *  <span class="term">hl_bal</span> - balance tags and ensure proper nesting<br />
2260   *  <span class="term">hl_cmtcd</span> - handle CDATA sections and HTML comments<br />
2261   *  <span class="term">hl_ent</span> - handle character entities<br />
2262   *  <span class="term">hl_prot</span> - check a URL scheme/protocol<br />
2263   *  <span class="term">hl_regex</span> - check syntax of a regular expression<br />
2264   *  <span class="term">hl_spec</span> - convert user-supplied <span class="term">$spec</span> value to one used internally<br />
2265   *  <span class="term">hl_tag</span> - handle element tags and attributes<br />
2266   *  <span class="term">hl_tag2</span> - transform element tags<br />
2267   *  <span class="term">hl_tidy</span> - compact/beautify HTML<br />
2268   *  <span class="term">hl_version</span> - report htmLawed version<br />
2269   *  <span class="term">htmLawed</span> - main function<br />
2271   <span class="term">htmLawed()</span> finalizes <span class="term">$spec</span> (with the help of <span class="term">hl_spec()</span>) and <span class="term">$config</span>, and globalizes them. Finalization of <span class="term">$config</span> involves setting default values if an inappropriate or invalid one is supplied. This includes calling <span class="term">hl_regex()</span> to check well-formedness of regular expression patterns if such expressions are user-supplied through <span class="term">$config</span>. <span class="term">htmLawed()</span> then removes invalid characters like nulls and <span class="term">x01</span> and appropriately handles entities using <span class="term">hl_ent()</span>. HTML comments and CDATA sections are identified and treated as per <span class="term">$config</span> with the help of <span class="term">hl_cmtcd()</span>. When retained, the <span class="term"><</span> and <span class="term">></span> characters identifying them, and the <span class="term"><</span>, <span class="term">></span> and <span class="term">&</span> characters inside them, are replaced with control characters (code-points <span class="term">1</span> to <span class="term">5</span>) till any tag balancing is completed.<br />
2273   After this <em>initial processing</em> <span class="term">htmLawed()</span> identifies tags using regex and processes them with the help of <span class="term">hl_tag()</span> --  a large function that analyzes tag content, filtering it as per HTML standards, <span class="term">$config</span> and <span class="term">$spec</span>. Among other things, <span class="term">hl_tag()</span> transforms deprecated elements using <span class="term">hl_tag2()</span>, removes attributes from closing tags, checks attribute values as per <span class="term">$spec</span> rules using <span class="term">hl_attrval()</span>, and checks URL protocols using <span class="term">hl_prot()</span>. <span class="term">htmLawed()</span> performs tag balancing and nesting checks with a call to <span class="term">hl_bal()</span>, and optionally compacts/beautifies the output with proper white-spacing with a call to <span class="term">hl_tidy()</span>. The latter temporarily replaces white-space, and <span class="term"><</span>, <span class="term">></span> and <span class="term">&</span> characters inside <span class="term">pre</span>, <span class="term">script</span> and <span class="term">textarea</span> elements, and HTML comments and CDATA sections with control characters (code-points <span class="term">1</span> to <span class="term">5</span>, and <span class="term">7</span>).<br />
2275   htmLawed permits the use of custom code or <strong>hook functions</strong> at two stages. The first, called inside <span class="term">htmLawed()</span>, allows the input text as well as the finalized <span class="term">$config</span> and <span class="term">$spec</span> values to be altered right after the initial processing (see <a href="#s3.7">section 3.7</a>). The second is called by <span class="term">hl_tag()</span> once the tag content is finalized (see <a href="#s3.4.9">section 3.4.9</a>).<br />
2277   The functionality of htmLawed is dictated by the external HTML standards. The code of htmLawed is thus written for a clear-cut aim, with not much concern for tweaking by other developers. The code is only minimally annotated with comments -- it is not meant to instruct. PHP developers familiar with the HTML specifications will see the logic, and others can always refer to the htmLawed documentation.
2281 <hr /><br /><br /><span class="subtle"><small>HTM version of <em><a href="htmLawed_README.txt">htmLawed_README.txt</a></em> generated on 12 Sep, 2017 using <a href="http://www.bioinformatics.org/phplabware/internal_utilities">rTxt2htm</a> from PHP Labware</small></span>
2282 </div><!-- ended div body -->
2283 </div><!-- ended div top -->
projects / yaffs-website / blob