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[yaffs-website] / vendor / michelf / php-markdown / Michelf / MarkdownExtra.php
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+<?php
+/**
+ * Markdown Extra - A text-to-HTML conversion tool for web writers
+ *
+ * @package   php-markdown
+ * @author    Michel Fortin <michel.fortin@michelf.com>
+ * @copyright 2004-2016 Michel Fortin <https://michelf.com/projects/php-markdown/>
+ * @copyright (Original Markdown) 2004-2006 John Gruber <https://daringfireball.net/projects/markdown/>
+ */
+
+namespace Michelf;
+
+/**
+ * Markdown Extra Parser Class
+ */
+class MarkdownExtra extends \Michelf\Markdown {
+       /**
+        * Configuration variables
+        */
+
+       /**
+        * Prefix for footnote ids.
+        * @var string
+        */
+       public $fn_id_prefix = "";
+       
+       /**
+        * Optional title attribute for footnote links and backlinks.
+        * @var string
+        */
+       public $fn_link_title     = "";
+       public $fn_backlink_title = "";
+       
+       /**
+        * Optional class attribute for footnote links and backlinks.
+        * @var string
+        */
+       public $fn_link_class     = "footnote-ref";
+       public $fn_backlink_class = "footnote-backref";
+
+       /**
+        * Content to be displayed within footnote backlinks. The default is '↩';
+        * the U+FE0E on the end is a Unicode variant selector used to prevent iOS
+        * from displaying the arrow character as an emoji.
+        * @var string
+        */
+       public $fn_backlink_html = '&#8617;&#xFE0E;';
+
+       /**
+        * Class name for table cell alignment (%% replaced left/center/right)
+        * For instance: 'go-%%' becomes 'go-left' or 'go-right' or 'go-center'
+        * If empty, the align attribute is used instead of a class name.
+        * @var string
+        */
+       public $table_align_class_tmpl = '';
+
+       /**
+        * Optional class prefix for fenced code block.
+        * @var string
+        */
+       public $code_class_prefix = "";
+
+       /**
+        * Class attribute for code blocks goes on the `code` tag;
+        * setting this to true will put attributes on the `pre` tag instead.
+        * @var boolean
+        */
+       public $code_attr_on_pre = false;
+
+       /**
+        * Predefined abbreviations.
+        * @var array
+        */
+       public $predef_abbr = array();
+
+       /**
+        * Parser implementation
+        */
+       
+       /**
+        * Constructor function. Initialize the parser object.
+        * @return void
+        */
+       public function __construct() {
+               // Add extra escapable characters before parent constructor 
+               // initialize the table.
+               $this->escape_chars .= ':|';
+               
+               // Insert extra document, block, and span transformations. 
+               // Parent constructor will do the sorting.
+               $this->document_gamut += array(
+                       "doFencedCodeBlocks" => 5,
+                       "stripFootnotes"     => 15,
+                       "stripAbbreviations" => 25,
+                       "appendFootnotes"    => 50,
+               );
+               $this->block_gamut += array(
+                       "doFencedCodeBlocks" => 5,
+                       "doTables"           => 15,
+                       "doDefLists"         => 45,
+               );
+               $this->span_gamut += array(
+                       "doFootnotes"        => 5,
+                       "doAbbreviations"    => 70,
+               );
+               
+               $this->enhanced_ordered_list = true;
+               parent::__construct();
+       }
+       
+       
+       /**
+        * Extra variables used during extra transformations.
+        * @var array
+        */
+       protected $footnotes = array();
+       protected $footnotes_ordered = array();
+       protected $footnotes_ref_count = array();
+       protected $footnotes_numbers = array();
+       protected $abbr_desciptions = array();
+       /** @var @string */
+       protected $abbr_word_re = '';
+       
+       /**
+        * Give the current footnote number.
+        * @var integer
+        */
+       protected $footnote_counter = 1;
+       
+       /**
+        * Setting up Extra-specific variables.
+        */
+       protected function setup() {
+               parent::setup();
+               
+               $this->footnotes = array();
+               $this->footnotes_ordered = array();
+               $this->footnotes_ref_count = array();
+               $this->footnotes_numbers = array();
+               $this->abbr_desciptions = array();
+               $this->abbr_word_re = '';
+               $this->footnote_counter = 1;
+               
+               foreach ($this->predef_abbr as $abbr_word => $abbr_desc) {
+                       if ($this->abbr_word_re)
+                               $this->abbr_word_re .= '|';
+                       $this->abbr_word_re .= preg_quote($abbr_word);
+                       $this->abbr_desciptions[$abbr_word] = trim($abbr_desc);
+               }
+       }
+
+       /**
+        * Clearing Extra-specific variables.
+        */
+       protected function teardown() {
+               $this->footnotes = array();
+               $this->footnotes_ordered = array();
+               $this->footnotes_ref_count = array();
+               $this->footnotes_numbers = array();
+               $this->abbr_desciptions = array();
+               $this->abbr_word_re = '';
+               
+               parent::teardown();
+       }
+       
+       
+       /**
+        * Extra attribute parser
+        */
+
+       /**
+        * Expression to use to catch attributes (includes the braces)
+        * @var string
+        */
+       protected $id_class_attr_catch_re = '\{((?>[ ]*[#.a-z][-_:a-zA-Z0-9=]+){1,})[ ]*\}';
+
+       /**
+        * Expression to use when parsing in a context when no capture is desired
+        * @var string
+        */
+       protected $id_class_attr_nocatch_re = '\{(?>[ ]*[#.a-z][-_:a-zA-Z0-9=]+){1,}[ ]*\}';
+
+       /**
+        * Parse attributes caught by the $this->id_class_attr_catch_re expression
+        * and return the HTML-formatted list of attributes.
+        *
+        * Currently supported attributes are .class and #id.
+        *
+        * In addition, this method also supports supplying a default Id value,
+        * which will be used to populate the id attribute in case it was not
+        * overridden.
+        * @param  string $tag_name
+        * @param  string $attr
+        * @param  mixed  $defaultIdValue
+        * @param  array  $classes
+        * @return string
+        */
+       protected function doExtraAttributes($tag_name, $attr, $defaultIdValue = null, $classes = array()) {
+               if (empty($attr) && !$defaultIdValue && empty($classes)) return "";
+               
+               // Split on components
+               preg_match_all('/[#.a-z][-_:a-zA-Z0-9=]+/', $attr, $matches);
+               $elements = $matches[0];
+
+               // Handle classes and IDs (only first ID taken into account)
+               $attributes = array();
+               $id = false;
+               foreach ($elements as $element) {
+                       if ($element{0} == '.') {
+                               $classes[] = substr($element, 1);
+                       } else if ($element{0} == '#') {
+                               if ($id === false) $id = substr($element, 1);
+                       } else if (strpos($element, '=') > 0) {
+                               $parts = explode('=', $element, 2);
+                               $attributes[] = $parts[0] . '="' . $parts[1] . '"';
+                       }
+               }
+
+               if (!$id) $id = $defaultIdValue;
+
+               // Compose attributes as string
+               $attr_str = "";
+               if (!empty($id)) {
+                       $attr_str .= ' id="'.$this->encodeAttribute($id) .'"';
+               }
+               if (!empty($classes)) {
+                       $attr_str .= ' class="'. implode(" ", $classes) . '"';
+               }
+               if (!$this->no_markup && !empty($attributes)) {
+                       $attr_str .= ' '.implode(" ", $attributes);
+               }
+               return $attr_str;
+       }
+
+       /**
+        * Strips link definitions from text, stores the URLs and titles in
+        * hash references.
+        * @param  string $text
+        * @return string
+        */
+       protected function stripLinkDefinitions($text) {
+               $less_than_tab = $this->tab_width - 1;
+
+               // Link defs are in the form: ^[id]: url "optional title"
+               $text = preg_replace_callback('{
+                                                       ^[ ]{0,'.$less_than_tab.'}\[(.+)\][ ]?: # id = $1
+                                                         [ ]*
+                                                         \n?                           # maybe *one* newline
+                                                         [ ]*
+                                                       (?:
+                                                         <(.+?)>                       # url = $2
+                                                       |
+                                                         (\S+?)                        # url = $3
+                                                       )
+                                                         [ ]*
+                                                         \n?                           # maybe one newline
+                                                         [ ]*
+                                                       (?:
+                                                               (?<=\s)                 # lookbehind for whitespace
+                                                               ["(]
+                                                               (.*?)                   # title = $4
+                                                               [")]
+                                                               [ ]*
+                                                       )?      # title is optional
+                                       (?:[ ]* '.$this->id_class_attr_catch_re.' )?  # $5 = extra id & class attr
+                                                       (?:\n+|\Z)
+                       }xm',
+                       array($this, '_stripLinkDefinitions_callback'),
+                       $text);
+               return $text;
+       }
+
+       /**
+        * Strip link definition callback
+        * @param  array $matches
+        * @return string
+        */
+       protected function _stripLinkDefinitions_callback($matches) {
+               $link_id = strtolower($matches[1]);
+               $url = $matches[2] == '' ? $matches[3] : $matches[2];
+               $this->urls[$link_id] = $url;
+               $this->titles[$link_id] =& $matches[4];
+               $this->ref_attr[$link_id] = $this->doExtraAttributes("", $dummy =& $matches[5]);
+               return ''; // String that will replace the block
+       }
+
+
+       /**
+        * HTML block parser
+        */
+       
+       /**
+        * Tags that are always treated as block tags
+        * @var string
+        */
+       protected $block_tags_re = 'p|div|h[1-6]|blockquote|pre|table|dl|ol|ul|address|form|fieldset|iframe|hr|legend|article|section|nav|aside|hgroup|header|footer|figcaption|figure';
+                                                  
+       /**
+        * Tags treated as block tags only if the opening tag is alone on its line
+        * @var string
+        */
+       protected $context_block_tags_re = 'script|noscript|style|ins|del|iframe|object|source|track|param|math|svg|canvas|audio|video';
+       
+       /**
+        * Tags where markdown="1" default to span mode:
+        * @var string
+        */
+       protected $contain_span_tags_re = 'p|h[1-6]|li|dd|dt|td|th|legend|address';
+       
+       /**
+        * Tags which must not have their contents modified, no matter where
+        * they appear
+        * @var string
+        */
+       protected $clean_tags_re = 'script|style|math|svg';
+       
+       /**
+        * Tags that do not need to be closed.
+        * @var string
+        */
+       protected $auto_close_tags_re = 'hr|img|param|source|track';
+       
+       /**
+        * Hashify HTML Blocks and "clean tags".
+        *
+        * We only want to do this for block-level HTML tags, such as headers,
+        * lists, and tables. That's because we still want to wrap <p>s around
+        * "paragraphs" that are wrapped in non-block-level tags, such as anchors,
+        * phrase emphasis, and spans. The list of tags we're looking for is
+        * hard-coded.
+        *
+        * This works by calling _HashHTMLBlocks_InMarkdown, which then calls
+        * _HashHTMLBlocks_InHTML when it encounter block tags. When the markdown="1" 
+        * attribute is found within a tag, _HashHTMLBlocks_InHTML calls back
+        *  _HashHTMLBlocks_InMarkdown to handle the Markdown syntax within the tag.
+        * These two functions are calling each other. It's recursive!
+        * @param  string $text
+        * @return string
+        */
+       protected function hashHTMLBlocks($text) {
+               if ($this->no_markup) {
+                       return $text;
+               }
+
+               // Call the HTML-in-Markdown hasher.
+               list($text, ) = $this->_hashHTMLBlocks_inMarkdown($text);
+               
+               return $text;
+       }
+
+       /**
+        * Parse markdown text, calling _HashHTMLBlocks_InHTML for block tags.
+        *
+        * *   $indent is the number of space to be ignored when checking for code 
+        *     blocks. This is important because if we don't take the indent into 
+        *     account, something like this (which looks right) won't work as expected:
+        *
+        *     <div>
+        *         <div markdown="1">
+        *         Hello World.  <-- Is this a Markdown code block or text?
+        *         </div>  <-- Is this a Markdown code block or a real tag?
+        *     <div>
+        *
+        *     If you don't like this, just don't indent the tag on which
+        *     you apply the markdown="1" attribute.
+        *
+        * *   If $enclosing_tag_re is not empty, stops at the first unmatched closing 
+        *     tag with that name. Nested tags supported.
+        *
+        * *   If $span is true, text inside must treated as span. So any double 
+        *     newline will be replaced by a single newline so that it does not create 
+        *     paragraphs.
+        *
+        * Returns an array of that form: ( processed text , remaining text )
+        *
+        * @param  string  $text
+        * @param  integer $indent
+        * @param  string  $enclosing_tag_re
+        * @param  boolean $span
+        * @return array
+        */
+       protected function _hashHTMLBlocks_inMarkdown($text, $indent = 0,
+                                                                               $enclosing_tag_re = '', $span = false)
+       {
+       
+               if ($text === '') return array('', '');
+
+               // Regex to check for the presense of newlines around a block tag.
+               $newline_before_re = '/(?:^\n?|\n\n)*$/';
+               $newline_after_re = 
+                       '{
+                               ^                                               # Start of text following the tag.
+                               (?>[ ]*<!--.*?-->)?             # Optional comment.
+                               [ ]*\n                                  # Must be followed by newline.
+                       }xs';
+               
+               // Regex to match any tag.
+               $block_tag_re =
+                       '{
+                               (                                       # $2: Capture whole tag.
+                                       </?                                     # Any opening or closing tag.
+                                               (?>                             # Tag name.
+                                                       ' . $this->block_tags_re . '                    |
+                                                       ' . $this->context_block_tags_re . '    |
+                                                       ' . $this->clean_tags_re . '            |
+                                                       (?!\s)'.$enclosing_tag_re . '
+                                               )
+                                               (?:
+                                                       (?=[\s"\'/a-zA-Z0-9])   # Allowed characters after tag name.
+                                                       (?>
+                                                               ".*?"           |       # Double quotes (can contain `>`)
+                                                               \'.*?\'         |       # Single quotes (can contain `>`)
+                                                               .+?                             # Anything but quotes and `>`.
+                                                       )*?
+                                               )?
+                                       >                                       # End of tag.
+                               |
+                                       <!--    .*?     -->     # HTML Comment
+                               |
+                                       <\?.*?\?> | <%.*?%>     # Processing instruction
+                               |
+                                       <!\[CDATA\[.*?\]\]>     # CData Block
+                               ' . ( !$span ? ' # If not in span.
+                               |
+                                       # Indented code block
+                                       (?: ^[ ]*\n | ^ | \n[ ]*\n )
+                                       [ ]{' . ($indent + 4) . '}[^\n]* \n
+                                       (?>
+                                               (?: [ ]{' . ($indent + 4) . '}[^\n]* | [ ]* ) \n
+                                       )*
+                               |
+                                       # Fenced code block marker
+                                       (?<= ^ | \n )
+                                       [ ]{0,' . ($indent + 3) . '}(?:~{3,}|`{3,})
+                                       [ ]*
+                                       (?: \.?[-_:a-zA-Z0-9]+ )? # standalone class name
+                                       [ ]*
+                                       (?: ' . $this->id_class_attr_nocatch_re . ' )? # extra attributes
+                                       [ ]*
+                                       (?= \n )
+                               ' : '' ) . ' # End (if not is span).
+                               |
+                                       # Code span marker
+                                       # Note, this regex needs to go after backtick fenced
+                                       # code blocks but it should also be kept outside of the
+                                       # "if not in span" condition adding backticks to the parser
+                                       `+
+                               )
+                       }xs';
+
+               
+               $depth = 0;             // Current depth inside the tag tree.
+               $parsed = "";   // Parsed text that will be returned.
+
+               // Loop through every tag until we find the closing tag of the parent
+               // or loop until reaching the end of text if no parent tag specified.
+               do {
+                       // Split the text using the first $tag_match pattern found.
+                       // Text before  pattern will be first in the array, text after
+                       // pattern will be at the end, and between will be any catches made 
+                       // by the pattern.
+                       $parts = preg_split($block_tag_re, $text, 2, 
+                                                               PREG_SPLIT_DELIM_CAPTURE);
+                       
+                       // If in Markdown span mode, add a empty-string span-level hash 
+                       // after each newline to prevent triggering any block element.
+                       if ($span) {
+                               $void = $this->hashPart("", ':');
+                               $newline = "\n$void";
+                               $parts[0] = $void . str_replace("\n", $newline, $parts[0]) . $void;
+                       }
+                       
+                       $parsed .= $parts[0]; // Text before current tag.
+                       
+                       // If end of $text has been reached. Stop loop.
+                       if (count($parts) < 3) {
+                               $text = "";
+                               break;
+                       }
+                       
+                       $tag  = $parts[1]; // Tag to handle.
+                       $text = $parts[2]; // Remaining text after current tag.
+                       $tag_re = preg_quote($tag); // For use in a regular expression.
+                       
+                       // Check for: Fenced code block marker.
+                       // Note: need to recheck the whole tag to disambiguate backtick
+                       // fences from code spans
+                       if (preg_match('{^\n?([ ]{0,' . ($indent + 3) . '})(~{3,}|`{3,})[ ]*(?:\.?[-_:a-zA-Z0-9]+)?[ ]*(?:' . $this->id_class_attr_nocatch_re . ')?[ ]*\n?$}', $tag, $capture)) {
+                               // Fenced code block marker: find matching end marker.
+                               $fence_indent = strlen($capture[1]); // use captured indent in re
+                               $fence_re = $capture[2]; // use captured fence in re
+                               if (preg_match('{^(?>.*\n)*?[ ]{' . ($fence_indent) . '}' . $fence_re . '[ ]*(?:\n|$)}', $text,
+                                       $matches)) 
+                               {
+                                       // End marker found: pass text unchanged until marker.
+                                       $parsed .= $tag . $matches[0];
+                                       $text = substr($text, strlen($matches[0]));
+                               }
+                               else {
+                                       // No end marker: just skip it.
+                                       $parsed .= $tag;
+                               }
+                       }
+                       // Check for: Indented code block.
+                       else if ($tag{0} == "\n" || $tag{0} == " ") {
+                               // Indented code block: pass it unchanged, will be handled 
+                               // later.
+                               $parsed .= $tag;
+                       }
+                       // Check for: Code span marker
+                       // Note: need to check this after backtick fenced code blocks
+                       else if ($tag{0} == "`") {
+                               // Find corresponding end marker.
+                               $tag_re = preg_quote($tag);
+                               if (preg_match('{^(?>.+?|\n(?!\n))*?(?<!`)' . $tag_re . '(?!`)}',
+                                       $text, $matches))
+                               {
+                                       // End marker found: pass text unchanged until marker.
+                                       $parsed .= $tag . $matches[0];
+                                       $text = substr($text, strlen($matches[0]));
+                               }
+                               else {
+                                       // Unmatched marker: just skip it.
+                                       $parsed .= $tag;
+                               }
+                       }
+                       // Check for: Opening Block level tag or
+                       //            Opening Context Block tag (like ins and del) 
+                       //               used as a block tag (tag is alone on it's line).
+                       else if (preg_match('{^<(?:' . $this->block_tags_re . ')\b}', $tag) ||
+                               (       preg_match('{^<(?:' . $this->context_block_tags_re . ')\b}', $tag) &&
+                                       preg_match($newline_before_re, $parsed) &&
+                                       preg_match($newline_after_re, $text)    )
+                               )
+                       {
+                               // Need to parse tag and following text using the HTML parser.
+                               list($block_text, $text) = 
+                                       $this->_hashHTMLBlocks_inHTML($tag . $text, "hashBlock", true);
+                               
+                               // Make sure it stays outside of any paragraph by adding newlines.
+                               $parsed .= "\n\n$block_text\n\n";
+                       }
+                       // Check for: Clean tag (like script, math)
+                       //            HTML Comments, processing instructions.
+                       else if (preg_match('{^<(?:' . $this->clean_tags_re . ')\b}', $tag) ||
+                               $tag{1} == '!' || $tag{1} == '?')
+                       {
+                               // Need to parse tag and following text using the HTML parser.
+                               // (don't check for markdown attribute)
+                               list($block_text, $text) = 
+                                       $this->_hashHTMLBlocks_inHTML($tag . $text, "hashClean", false);
+                               
+                               $parsed .= $block_text;
+                       }
+                       // Check for: Tag with same name as enclosing tag.
+                       else if ($enclosing_tag_re !== '' &&
+                               // Same name as enclosing tag.
+                               preg_match('{^</?(?:' . $enclosing_tag_re . ')\b}', $tag))
+                       {
+                               // Increase/decrease nested tag count.
+                               if ($tag{1} == '/')                                             $depth--;
+                               else if ($tag{strlen($tag)-2} != '/')   $depth++;
+
+                               if ($depth < 0) {
+                                       // Going out of parent element. Clean up and break so we
+                                       // return to the calling function.
+                                       $text = $tag . $text;
+                                       break;
+                               }
+                               
+                               $parsed .= $tag;
+                       }
+                       else {
+                               $parsed .= $tag;
+                       }
+               } while ($depth >= 0);
+               
+               return array($parsed, $text);
+       }
+
+       /**
+        * Parse HTML, calling _HashHTMLBlocks_InMarkdown for block tags.
+        *
+        * *   Calls $hash_method to convert any blocks.
+        * *   Stops when the first opening tag closes.
+        * *   $md_attr indicate if the use of the `markdown="1"` attribute is allowed.
+        *     (it is not inside clean tags)
+        *
+        * Returns an array of that form: ( processed text , remaining text )
+        * @param  string $text
+        * @param  string $hash_method
+        * @param  string $md_attr
+        * @return array
+        */
+       protected function _hashHTMLBlocks_inHTML($text, $hash_method, $md_attr) {
+               if ($text === '') return array('', '');
+               
+               // Regex to match `markdown` attribute inside of a tag.
+               $markdown_attr_re = '
+                       {
+                               \s*                     # Eat whitespace before the `markdown` attribute
+                               markdown
+                               \s*=\s*
+                               (?>
+                                       (["\'])         # $1: quote delimiter           
+                                       (.*?)           # $2: attribute value
+                                       \1                      # matching delimiter    
+                               |
+                                       ([^\s>]*)       # $3: unquoted attribute value
+                               )
+                               ()                              # $4: make $3 always defined (avoid warnings)
+                       }xs';
+               
+               // Regex to match any tag.
+               $tag_re = '{
+                               (                                       # $2: Capture whole tag.
+                                       </?                                     # Any opening or closing tag.
+                                               [\w:$]+                 # Tag name.
+                                               (?:
+                                                       (?=[\s"\'/a-zA-Z0-9])   # Allowed characters after tag name.
+                                                       (?>
+                                                               ".*?"           |       # Double quotes (can contain `>`)
+                                                               \'.*?\'         |       # Single quotes (can contain `>`)
+                                                               .+?                             # Anything but quotes and `>`.
+                                                       )*?
+                                               )?
+                                       >                                       # End of tag.
+                               |
+                                       <!--    .*?     -->     # HTML Comment
+                               |
+                                       <\?.*?\?> | <%.*?%>     # Processing instruction
+                               |
+                                       <!\[CDATA\[.*?\]\]>     # CData Block
+                               )
+                       }xs';
+               
+               $original_text = $text;         // Save original text in case of faliure.
+               
+               $depth          = 0;    // Current depth inside the tag tree.
+               $block_text     = "";   // Temporary text holder for current text.
+               $parsed         = "";   // Parsed text that will be returned.
+
+               // Get the name of the starting tag.
+               // (This pattern makes $base_tag_name_re safe without quoting.)
+               if (preg_match('/^<([\w:$]*)\b/', $text, $matches))
+                       $base_tag_name_re = $matches[1];
+
+               // Loop through every tag until we find the corresponding closing tag.
+               do {
+                       // Split the text using the first $tag_match pattern found.
+                       // Text before  pattern will be first in the array, text after
+                       // pattern will be at the end, and between will be any catches made 
+                       // by the pattern.
+                       $parts = preg_split($tag_re, $text, 2, PREG_SPLIT_DELIM_CAPTURE);
+                       
+                       if (count($parts) < 3) {
+                               // End of $text reached with unbalenced tag(s).
+                               // In that case, we return original text unchanged and pass the
+                               // first character as filtered to prevent an infinite loop in the 
+                               // parent function.
+                               return array($original_text{0}, substr($original_text, 1));
+                       }
+                       
+                       $block_text .= $parts[0]; // Text before current tag.
+                       $tag         = $parts[1]; // Tag to handle.
+                       $text        = $parts[2]; // Remaining text after current tag.
+                       
+                       // Check for: Auto-close tag (like <hr/>)
+                       //                       Comments and Processing Instructions.
+                       if (preg_match('{^</?(?:' . $this->auto_close_tags_re . ')\b}', $tag) ||
+                               $tag{1} == '!' || $tag{1} == '?')
+                       {
+                               // Just add the tag to the block as if it was text.
+                               $block_text .= $tag;
+                       }
+                       else {
+                               // Increase/decrease nested tag count. Only do so if
+                               // the tag's name match base tag's.
+                               if (preg_match('{^</?' . $base_tag_name_re . '\b}', $tag)) {
+                                       if ($tag{1} == '/')                                             $depth--;
+                                       else if ($tag{strlen($tag)-2} != '/')   $depth++;
+                               }
+                               
+                               // Check for `markdown="1"` attribute and handle it.
+                               if ($md_attr && 
+                                       preg_match($markdown_attr_re, $tag, $attr_m) &&
+                                       preg_match('/^1|block|span$/', $attr_m[2] . $attr_m[3]))
+                               {
+                                       // Remove `markdown` attribute from opening tag.
+                                       $tag = preg_replace($markdown_attr_re, '', $tag);
+                                       
+                                       // Check if text inside this tag must be parsed in span mode.
+                                       $this->mode = $attr_m[2] . $attr_m[3];
+                                       $span_mode = $this->mode == 'span' || $this->mode != 'block' &&
+                                               preg_match('{^<(?:' . $this->contain_span_tags_re . ')\b}', $tag);
+                                       
+                                       // Calculate indent before tag.
+                                       if (preg_match('/(?:^|\n)( *?)(?! ).*?$/', $block_text, $matches)) {
+                                               $strlen = $this->utf8_strlen;
+                                               $indent = $strlen($matches[1], 'UTF-8');
+                                       } else {
+                                               $indent = 0;
+                                       }
+                                       
+                                       // End preceding block with this tag.
+                                       $block_text .= $tag;
+                                       $parsed .= $this->$hash_method($block_text);
+                                       
+                                       // Get enclosing tag name for the ParseMarkdown function.
+                                       // (This pattern makes $tag_name_re safe without quoting.)
+                                       preg_match('/^<([\w:$]*)\b/', $tag, $matches);
+                                       $tag_name_re = $matches[1];
+                                       
+                                       // Parse the content using the HTML-in-Markdown parser.
+                                       list ($block_text, $text)
+                                               = $this->_hashHTMLBlocks_inMarkdown($text, $indent, 
+                                                       $tag_name_re, $span_mode);
+                                       
+                                       // Outdent markdown text.
+                                       if ($indent > 0) {
+                                               $block_text = preg_replace("/^[ ]{1,$indent}/m", "", 
+                                                                                                       $block_text);
+                                       }
+                                       
+                                       // Append tag content to parsed text.
+                                       if (!$span_mode)        $parsed .= "\n\n$block_text\n\n";
+                                       else                            $parsed .= "$block_text";
+                                       
+                                       // Start over with a new block.
+                                       $block_text = "";
+                               }
+                               else $block_text .= $tag;
+                       }
+                       
+               } while ($depth > 0);
+               
+               // Hash last block text that wasn't processed inside the loop.
+               $parsed .= $this->$hash_method($block_text);
+               
+               return array($parsed, $text);
+       }
+
+       /**
+        * Called whenever a tag must be hashed when a function inserts a "clean" tag
+        * in $text, it passes through this function and is automaticaly escaped, 
+        * blocking invalid nested overlap.
+        * @param  string $text
+        * @return string
+        */
+       protected function hashClean($text) {
+               return $this->hashPart($text, 'C');
+       }
+
+       /**
+        * Turn Markdown link shortcuts into XHTML <a> tags.
+        * @param  string $text
+        * @return string
+        */
+       protected function doAnchors($text) {
+               if ($this->in_anchor) {
+                       return $text;
+               }
+               $this->in_anchor = true;
+
+               // First, handle reference-style links: [link text] [id]
+               $text = preg_replace_callback('{
+                       (                                       # wrap whole match in $1
+                         \[
+                               (' . $this->nested_brackets_re . ')     # link text = $2
+                         \]
+
+                         [ ]?                          # one optional space
+                         (?:\n[ ]*)?           # one optional newline followed by spaces
+
+                         \[
+                               (.*?)           # id = $3
+                         \]
+                       )
+                       }xs',
+                       array($this, '_doAnchors_reference_callback'), $text);
+
+               // Next, inline-style links: [link text](url "optional title")
+               $text = preg_replace_callback('{
+                       (                               # wrap whole match in $1
+                         \[
+                               (' . $this->nested_brackets_re . ')     # link text = $2
+                         \]
+                         \(                    # literal paren
+                               [ \n]*
+                               (?:
+                                       <(.+?)> # href = $3
+                               |
+                                       (' . $this->nested_url_parenthesis_re . ')      # href = $4
+                               )
+                               [ \n]*
+                               (                       # $5
+                                 ([\'"])       # quote char = $6
+                                 (.*?)         # Title = $7
+                                 \6            # matching quote
+                                 [ \n]*        # ignore any spaces/tabs between closing quote and )
+                               )?                      # title is optional
+                         \)
+                         (?:[ ]? ' . $this->id_class_attr_catch_re . ' )?       # $8 = id/class attributes
+                       )
+                       }xs',
+                       array($this, '_doAnchors_inline_callback'), $text);
+
+               // Last, handle reference-style shortcuts: [link text]
+               // These must come last in case you've also got [link text][1]
+               // or [link text](/foo)
+               $text = preg_replace_callback('{
+                       (                                       # wrap whole match in $1
+                         \[
+                               ([^\[\]]+)              # link text = $2; can\'t contain [ or ]
+                         \]
+                       )
+                       }xs',
+                       array($this, '_doAnchors_reference_callback'), $text);
+
+               $this->in_anchor = false;
+               return $text;
+       }
+
+       /**
+        * Callback for reference anchors
+        * @param  array $matches
+        * @return string
+        */
+       protected function _doAnchors_reference_callback($matches) {
+               $whole_match =  $matches[1];
+               $link_text   =  $matches[2];
+               $link_id     =& $matches[3];
+
+               if ($link_id == "") {
+                       // for shortcut links like [this][] or [this].
+                       $link_id = $link_text;
+               }
+               
+               // lower-case and turn embedded newlines into spaces
+               $link_id = strtolower($link_id);
+               $link_id = preg_replace('{[ ]?\n}', ' ', $link_id);
+
+               if (isset($this->urls[$link_id])) {
+                       $url = $this->urls[$link_id];
+                       $url = $this->encodeURLAttribute($url);
+                       
+                       $result = "<a href=\"$url\"";
+                       if ( isset( $this->titles[$link_id] ) ) {
+                               $title = $this->titles[$link_id];
+                               $title = $this->encodeAttribute($title);
+                               $result .=  " title=\"$title\"";
+                       }
+                       if (isset($this->ref_attr[$link_id]))
+                               $result .= $this->ref_attr[$link_id];
+               
+                       $link_text = $this->runSpanGamut($link_text);
+                       $result .= ">$link_text</a>";
+                       $result = $this->hashPart($result);
+               }
+               else {
+                       $result = $whole_match;
+               }
+               return $result;
+       }
+
+       /**
+        * Callback for inline anchors
+        * @param  array $matches
+        * @return string
+        */
+       protected function _doAnchors_inline_callback($matches) {
+               $whole_match    =  $matches[1];
+               $link_text              =  $this->runSpanGamut($matches[2]);
+               $url                    =  $matches[3] == '' ? $matches[4] : $matches[3];
+               $title                  =& $matches[7];
+               $attr  = $this->doExtraAttributes("a", $dummy =& $matches[8]);
+
+               // if the URL was of the form <s p a c e s> it got caught by the HTML
+               // tag parser and hashed. Need to reverse the process before using the URL.
+               $unhashed = $this->unhash($url);
+               if ($unhashed != $url)
+                       $url = preg_replace('/^<(.*)>$/', '\1', $unhashed);
+
+               $url = $this->encodeURLAttribute($url);
+
+               $result = "<a href=\"$url\"";
+               if (isset($title)) {
+                       $title = $this->encodeAttribute($title);
+                       $result .=  " title=\"$title\"";
+               }
+               $result .= $attr;
+               
+               $link_text = $this->runSpanGamut($link_text);
+               $result .= ">$link_text</a>";
+
+               return $this->hashPart($result);
+       }
+
+       /**
+        * Turn Markdown image shortcuts into <img> tags.
+        * @param  string $text
+        * @return string
+        */
+       protected function doImages($text) {
+               // First, handle reference-style labeled images: ![alt text][id]
+               $text = preg_replace_callback('{
+                       (                               # wrap whole match in $1
+                         !\[
+                               (' . $this->nested_brackets_re . ')             # alt text = $2
+                         \]
+
+                         [ ]?                          # one optional space
+                         (?:\n[ ]*)?           # one optional newline followed by spaces
+
+                         \[
+                               (.*?)           # id = $3
+                         \]
+
+                       )
+                       }xs', 
+                       array($this, '_doImages_reference_callback'), $text);
+
+               // Next, handle inline images:  ![alt text](url "optional title")
+               // Don't forget: encode * and _
+               $text = preg_replace_callback('{
+                       (                               # wrap whole match in $1
+                         !\[
+                               (' . $this->nested_brackets_re . ')             # alt text = $2
+                         \]
+                         \s?                   # One optional whitespace character
+                         \(                    # literal paren
+                               [ \n]*
+                               (?:
+                                       <(\S*)> # src url = $3
+                               |
+                                       (' . $this->nested_url_parenthesis_re . ')      # src url = $4
+                               )
+                               [ \n]*
+                               (                       # $5
+                                 ([\'"])       # quote char = $6
+                                 (.*?)         # title = $7
+                                 \6            # matching quote
+                                 [ \n]*
+                               )?                      # title is optional
+                         \)
+                         (?:[ ]? ' . $this->id_class_attr_catch_re . ' )?       # $8 = id/class attributes
+                       )
+                       }xs',
+                       array($this, '_doImages_inline_callback'), $text);
+
+               return $text;
+       }
+
+       /**
+        * Callback for referenced images
+        * @param  array $matches
+        * @return string
+        */
+       protected function _doImages_reference_callback($matches) {
+               $whole_match = $matches[1];
+               $alt_text    = $matches[2];
+               $link_id     = strtolower($matches[3]);
+
+               if ($link_id == "") {
+                       $link_id = strtolower($alt_text); // for shortcut links like ![this][].
+               }
+
+               $alt_text = $this->encodeAttribute($alt_text);
+               if (isset($this->urls[$link_id])) {
+                       $url = $this->encodeURLAttribute($this->urls[$link_id]);
+                       $result = "<img src=\"$url\" alt=\"$alt_text\"";
+                       if (isset($this->titles[$link_id])) {
+                               $title = $this->titles[$link_id];
+                               $title = $this->encodeAttribute($title);
+                               $result .=  " title=\"$title\"";
+                       }
+                       if (isset($this->ref_attr[$link_id]))
+                               $result .= $this->ref_attr[$link_id];
+                       $result .= $this->empty_element_suffix;
+                       $result = $this->hashPart($result);
+               }
+               else {
+                       // If there's no such link ID, leave intact:
+                       $result = $whole_match;
+               }
+
+               return $result;
+       }
+
+       /**
+        * Callback for inline images
+        * @param  array $matches
+        * @return string
+        */
+       protected function _doImages_inline_callback($matches) {
+               $whole_match    = $matches[1];
+               $alt_text               = $matches[2];
+               $url                    = $matches[3] == '' ? $matches[4] : $matches[3];
+               $title                  =& $matches[7];
+               $attr  = $this->doExtraAttributes("img", $dummy =& $matches[8]);
+
+               $alt_text = $this->encodeAttribute($alt_text);
+               $url = $this->encodeURLAttribute($url);
+               $result = "<img src=\"$url\" alt=\"$alt_text\"";
+               if (isset($title)) {
+                       $title = $this->encodeAttribute($title);
+                       $result .=  " title=\"$title\""; // $title already quoted
+               }
+               $result .= $attr;
+               $result .= $this->empty_element_suffix;
+
+               return $this->hashPart($result);
+       }
+
+       /**
+        * Process markdown headers. Redefined to add ID and class attribute support.
+        * @param  string $text
+        * @return string
+        */
+       protected function doHeaders($text) {
+               // Setext-style headers:
+               //  Header 1  {#header1}
+               //        ========
+               //  
+               //        Header 2  {#header2 .class1 .class2}
+               //        --------
+               //
+               $text = preg_replace_callback(
+                       '{
+                               (^.+?)                                                          # $1: Header text
+                               (?:[ ]+ ' . $this->id_class_attr_catch_re . ' )?         # $3 = id/class attributes
+                               [ ]*\n(=+|-+)[ ]*\n+                            # $3: Header footer
+                       }mx',
+                       array($this, '_doHeaders_callback_setext'), $text);
+
+               // atx-style headers:
+               //      # Header 1        {#header1}
+               //      ## Header 2       {#header2}
+               //      ## Header 2 with closing hashes ##  {#header3.class1.class2}
+               //      ...
+               //      ###### Header 6   {.class2}
+               //
+               $text = preg_replace_callback('{
+                               ^(\#{1,6})      # $1 = string of #\'s
+                               [ ]*
+                               (.+?)           # $2 = Header text
+                               [ ]*
+                               \#*                     # optional closing #\'s (not counted)
+                               (?:[ ]+ ' . $this->id_class_attr_catch_re . ' )?         # $3 = id/class attributes
+                               [ ]*
+                               \n+
+                       }xm',
+                       array($this, '_doHeaders_callback_atx'), $text);
+
+               return $text;
+       }
+
+       /**
+        * Callback for setext headers
+        * @param  array $matches
+        * @return string
+        */
+       protected function _doHeaders_callback_setext($matches) {
+               if ($matches[3] == '-' && preg_match('{^- }', $matches[1])) {
+                       return $matches[0];
+               }
+
+               $level = $matches[3]{0} == '=' ? 1 : 2;
+
+               $defaultId = is_callable($this->header_id_func) ? call_user_func($this->header_id_func, $matches[1]) : null;
+
+               $attr  = $this->doExtraAttributes("h$level", $dummy =& $matches[2], $defaultId);
+               $block = "<h$level$attr>" . $this->runSpanGamut($matches[1]) . "</h$level>";
+               return "\n" . $this->hashBlock($block) . "\n\n";
+       }
+
+       /**
+        * Callback for atx headers
+        * @param  array $matches
+        * @return string
+        */
+       protected function _doHeaders_callback_atx($matches) {
+               $level = strlen($matches[1]);
+
+               $defaultId = is_callable($this->header_id_func) ? call_user_func($this->header_id_func, $matches[2]) : null;
+               $attr  = $this->doExtraAttributes("h$level", $dummy =& $matches[3], $defaultId);
+               $block = "<h$level$attr>" . $this->runSpanGamut($matches[2]) . "</h$level>";
+               return "\n" . $this->hashBlock($block) . "\n\n";
+       }
+
+       /**
+        * Form HTML tables.
+        * @param  string $text
+        * @return string
+        */
+       protected function doTables($text) {
+               $less_than_tab = $this->tab_width - 1;
+               // Find tables with leading pipe.
+               //
+               //      | Header 1 | Header 2
+               //      | -------- | --------
+               //      | Cell 1   | Cell 2
+               //      | Cell 3   | Cell 4
+               $text = preg_replace_callback('
+                       {
+                               ^                                                       # Start of a line
+                               [ ]{0,' . $less_than_tab . '}   # Allowed whitespace.
+                               [|]                                                     # Optional leading pipe (present)
+                               (.+) \n                                         # $1: Header row (at least one pipe)
+                               
+                               [ ]{0,' . $less_than_tab . '}   # Allowed whitespace.
+                               [|] ([ ]*[-:]+[-| :]*) \n       # $2: Header underline
+                               
+                               (                                                       # $3: Cells
+                                       (?>
+                                               [ ]*                            # Allowed whitespace.
+                                               [|] .* \n                       # Row content.
+                                       )*
+                               )
+                               (?=\n|\Z)                                       # Stop at final double newline.
+                       }xm',
+                       array($this, '_doTable_leadingPipe_callback'), $text);
+
+               // Find tables without leading pipe.
+               //
+               //      Header 1 | Header 2
+               //      -------- | --------
+               //      Cell 1   | Cell 2
+               //      Cell 3   | Cell 4
+               $text = preg_replace_callback('
+                       {
+                               ^                                                       # Start of a line
+                               [ ]{0,' . $less_than_tab . '}   # Allowed whitespace.
+                               (\S.*[|].*) \n                          # $1: Header row (at least one pipe)
+                               
+                               [ ]{0,' . $less_than_tab . '}   # Allowed whitespace.
+                               ([-:]+[ ]*[|][-| :]*) \n        # $2: Header underline
+                               
+                               (                                                       # $3: Cells
+                                       (?>
+                                               .* [|] .* \n            # Row content
+                                       )*
+                               )
+                               (?=\n|\Z)                                       # Stop at final double newline.
+                       }xm',
+                       array($this, '_DoTable_callback'), $text);
+
+               return $text;
+       }
+
+       /**
+        * Callback for removing the leading pipe for each row
+        * @param  array $matches
+        * @return string
+        */
+       protected function _doTable_leadingPipe_callback($matches) {
+               $head           = $matches[1];
+               $underline      = $matches[2];
+               $content        = $matches[3];
+
+               $content        = preg_replace('/^ *[|]/m', '', $content);
+               
+               return $this->_doTable_callback(array($matches[0], $head, $underline, $content));
+       }
+
+       /**
+        * Make the align attribute in a table
+        * @param  string $alignname
+        * @return string
+        */
+       protected function _doTable_makeAlignAttr($alignname)
+       {
+               if (empty($this->table_align_class_tmpl)) {
+                       return " align=\"$alignname\"";
+               }
+
+               $classname = str_replace('%%', $alignname, $this->table_align_class_tmpl);
+               return " class=\"$classname\"";
+       }
+
+       /**
+        * Calback for processing tables
+        * @param  array $matches
+        * @return string
+        */
+       protected function _doTable_callback($matches) {
+               $head           = $matches[1];
+               $underline      = $matches[2];
+               $content        = $matches[3];
+
+               // Remove any tailing pipes for each line.
+               $head           = preg_replace('/[|] *$/m', '', $head);
+               $underline      = preg_replace('/[|] *$/m', '', $underline);
+               $content        = preg_replace('/[|] *$/m', '', $content);
+               
+               // Reading alignement from header underline.
+               $separators     = preg_split('/ *[|] */', $underline);
+               foreach ($separators as $n => $s) {
+                       if (preg_match('/^ *-+: *$/', $s))
+                               $attr[$n] = $this->_doTable_makeAlignAttr('right');
+                       else if (preg_match('/^ *:-+: *$/', $s))
+                               $attr[$n] = $this->_doTable_makeAlignAttr('center');
+                       else if (preg_match('/^ *:-+ *$/', $s))
+                               $attr[$n] = $this->_doTable_makeAlignAttr('left');
+                       else
+                               $attr[$n] = '';
+               }
+               
+               // Parsing span elements, including code spans, character escapes, 
+               // and inline HTML tags, so that pipes inside those gets ignored.
+               $head           = $this->parseSpan($head);
+               $headers        = preg_split('/ *[|] */', $head);
+               $col_count      = count($headers);
+               $attr       = array_pad($attr, $col_count, '');
+               
+               // Write column headers.
+               $text = "<table>\n";
+               $text .= "<thead>\n";
+               $text .= "<tr>\n";
+               foreach ($headers as $n => $header)
+                       $text .= "  <th$attr[$n]>" . $this->runSpanGamut(trim($header)) . "</th>\n";
+               $text .= "</tr>\n";
+               $text .= "</thead>\n";
+               
+               // Split content by row.
+               $rows = explode("\n", trim($content, "\n"));
+               
+               $text .= "<tbody>\n";
+               foreach ($rows as $row) {
+                       // Parsing span elements, including code spans, character escapes, 
+                       // and inline HTML tags, so that pipes inside those gets ignored.
+                       $row = $this->parseSpan($row);
+                       
+                       // Split row by cell.
+                       $row_cells = preg_split('/ *[|] */', $row, $col_count);
+                       $row_cells = array_pad($row_cells, $col_count, '');
+                       
+                       $text .= "<tr>\n";
+                       foreach ($row_cells as $n => $cell)
+                               $text .= "  <td$attr[$n]>" . $this->runSpanGamut(trim($cell)) . "</td>\n";
+                       $text .= "</tr>\n";
+               }
+               $text .= "</tbody>\n";
+               $text .= "</table>";
+               
+               return $this->hashBlock($text) . "\n";
+       }
+
+       /**
+        * Form HTML definition lists.
+        * @param  string $text
+        * @return string
+        */
+       protected function doDefLists($text) {
+               $less_than_tab = $this->tab_width - 1;
+
+               // Re-usable pattern to match any entire dl list:
+               $whole_list_re = '(?>
+                       (                                                               # $1 = whole list
+                         (                                                             # $2
+                               [ ]{0,' . $less_than_tab . '}
+                               ((?>.*\S.*\n)+)                         # $3 = defined term
+                               \n?
+                               [ ]{0,' . $less_than_tab . '}:[ ]+ # colon starting definition
+                         )
+                         (?s:.+?)
+                         (                                                             # $4
+                                 \z
+                               |
+                                 \n{2,}
+                                 (?=\S)
+                                 (?!                                           # Negative lookahead for another term
+                                       [ ]{0,' . $less_than_tab . '}
+                                       (?: \S.*\n )+?                  # defined term
+                                       \n?
+                                       [ ]{0,' . $less_than_tab . '}:[ ]+ # colon starting definition
+                                 )
+                                 (?!                                           # Negative lookahead for another definition
+                                       [ ]{0,' . $less_than_tab . '}:[ ]+ # colon starting definition
+                                 )
+                         )
+                       )
+               )'; // mx
+
+               $text = preg_replace_callback('{
+                               (?>\A\n?|(?<=\n\n))
+                               ' . $whole_list_re . '
+                       }mx',
+                       array($this, '_doDefLists_callback'), $text);
+
+               return $text;
+       }
+
+       /**
+        * Callback for processing definition lists
+        * @param  array $matches
+        * @return string
+        */
+       protected function _doDefLists_callback($matches) {
+               // Re-usable patterns to match list item bullets and number markers:
+               $list = $matches[1];
+               
+               // Turn double returns into triple returns, so that we can make a
+               // paragraph for the last item in a list, if necessary:
+               $result = trim($this->processDefListItems($list));
+               $result = "<dl>\n" . $result . "\n</dl>";
+               return $this->hashBlock($result) . "\n\n";
+       }
+
+       /**
+        * Process the contents of a single definition list, splitting it
+        * into individual term and definition list items.
+        * @param  string $list_str
+        * @return string
+        */
+       protected function processDefListItems($list_str) {
+       
+               $less_than_tab = $this->tab_width - 1;
+               
+               // Trim trailing blank lines:
+               $list_str = preg_replace("/\n{2,}\\z/", "\n", $list_str);
+
+               // Process definition terms.
+               $list_str = preg_replace_callback('{
+                       (?>\A\n?|\n\n+)                                         # leading line
+                       (                                                                       # definition terms = $1
+                               [ ]{0,' . $less_than_tab . '}   # leading whitespace
+                               (?!\:[ ]|[ ])                                   # negative lookahead for a definition
+                                                                                               #   mark (colon) or more whitespace.
+                               (?> \S.* \n)+?                                  # actual term (not whitespace). 
+                       )                       
+                       (?=\n?[ ]{0,3}:[ ])                                     # lookahead for following line feed 
+                                                                                               #   with a definition mark.
+                       }xm',
+                       array($this, '_processDefListItems_callback_dt'), $list_str);
+
+               // Process actual definitions.
+               $list_str = preg_replace_callback('{
+                       \n(\n+)?                                                        # leading line = $1
+                       (                                                                       # marker space = $2
+                               [ ]{0,' . $less_than_tab . '}   # whitespace before colon
+                               \:[ ]+                                                  # definition mark (colon)
+                       )
+                       ((?s:.+?))                                                      # definition text = $3
+                       (?= \n+                                                         # stop at next definition mark,
+                               (?:                                                             # next term or end of text
+                                       [ ]{0,' . $less_than_tab . '} \:[ ]     |
+                                       <dt> | \z
+                               )                                               
+                       )                                       
+                       }xm',
+                       array($this, '_processDefListItems_callback_dd'), $list_str);
+
+               return $list_str;
+       }
+
+       /**
+        * Callback for <dt> elements in definition lists
+        * @param  array $matches
+        * @return string
+        */
+       protected function _processDefListItems_callback_dt($matches) {
+               $terms = explode("\n", trim($matches[1]));
+               $text = '';
+               foreach ($terms as $term) {
+                       $term = $this->runSpanGamut(trim($term));
+                       $text .= "\n<dt>" . $term . "</dt>";
+               }
+               return $text . "\n";
+       }
+
+       /**
+        * Callback for <dd> elements in definition lists
+        * @param  array $matches
+        * @return string
+        */
+       protected function _processDefListItems_callback_dd($matches) {
+               $leading_line   = $matches[1];
+               $marker_space   = $matches[2];
+               $def                    = $matches[3];
+
+               if ($leading_line || preg_match('/\n{2,}/', $def)) {
+                       // Replace marker with the appropriate whitespace indentation
+                       $def = str_repeat(' ', strlen($marker_space)) . $def;
+                       $def = $this->runBlockGamut($this->outdent($def . "\n\n"));
+                       $def = "\n". $def ."\n";
+               }
+               else {
+                       $def = rtrim($def);
+                       $def = $this->runSpanGamut($this->outdent($def));
+               }
+
+               return "\n<dd>" . $def . "</dd>\n";
+       }
+
+       /**
+        * Adding the fenced code block syntax to regular Markdown:
+        *
+        * ~~~
+        * Code block
+        * ~~~
+        * 
+        * @param  string $text
+        * @return string
+        */
+       protected function doFencedCodeBlocks($text) {
+       
+               $less_than_tab = $this->tab_width;
+               
+               $text = preg_replace_callback('{
+                               (?:\n|\A)
+                               # 1: Opening marker
+                               (
+                                       (?:~{3,}|`{3,}) # 3 or more tildes/backticks.
+                               )
+                               [ ]*
+                               (?:
+                                       \.?([-_:a-zA-Z0-9]+) # 2: standalone class name
+                               )?
+                               [ ]*
+                               (?:
+                                       ' . $this->id_class_attr_catch_re . ' # 3: Extra attributes
+                               )?
+                               [ ]* \n # Whitespace and newline following marker.
+                               
+                               # 4: Content
+                               (
+                                       (?>
+                                               (?!\1 [ ]* \n)  # Not a closing marker.
+                                               .*\n+
+                                       )+
+                               )
+                               
+                               # Closing marker.
+                               \1 [ ]* (?= \n )
+                       }xm',
+                       array($this, '_doFencedCodeBlocks_callback'), $text);
+
+               return $text;
+       }
+
+       /**
+        * Callback to process fenced code blocks
+        * @param  array $matches
+        * @return string
+        */
+       protected function _doFencedCodeBlocks_callback($matches) {
+               $classname =& $matches[2];
+               $attrs     =& $matches[3];
+               $codeblock = $matches[4];
+
+               if ($this->code_block_content_func) {
+                       $codeblock = call_user_func($this->code_block_content_func, $codeblock, $classname);
+               } else {
+                       $codeblock = htmlspecialchars($codeblock, ENT_NOQUOTES);
+               }
+
+               $codeblock = preg_replace_callback('/^\n+/',
+                       array($this, '_doFencedCodeBlocks_newlines'), $codeblock);
+
+               $classes = array();
+               if ($classname != "") {
+                       if ($classname{0} == '.')
+                               $classname = substr($classname, 1);
+                       $classes[] = $this->code_class_prefix . $classname;
+               }
+               $attr_str = $this->doExtraAttributes($this->code_attr_on_pre ? "pre" : "code", $attrs, null, $classes);
+               $pre_attr_str  = $this->code_attr_on_pre ? $attr_str : '';
+               $code_attr_str = $this->code_attr_on_pre ? '' : $attr_str;
+               $codeblock  = "<pre$pre_attr_str><code$code_attr_str>$codeblock</code></pre>";
+               
+               return "\n\n".$this->hashBlock($codeblock)."\n\n";
+       }
+
+       /**
+        * Replace new lines in fenced code blocks
+        * @param  array $matches
+        * @return string
+        */
+       protected function _doFencedCodeBlocks_newlines($matches) {
+               return str_repeat("<br$this->empty_element_suffix", 
+                       strlen($matches[0]));
+       }
+
+       /**
+        * Redefining emphasis markers so that emphasis by underscore does not
+        * work in the middle of a word.
+        * @var array
+        */
+       protected $em_relist = array(
+               ''  => '(?:(?<!\*)\*(?!\*)|(?<![a-zA-Z0-9_])_(?!_))(?![\.,:;]?\s)',
+               '*' => '(?<![\s*])\*(?!\*)',
+               '_' => '(?<![\s_])_(?![a-zA-Z0-9_])',
+       );
+       protected $strong_relist = array(
+               ''   => '(?:(?<!\*)\*\*(?!\*)|(?<![a-zA-Z0-9_])__(?!_))(?![\.,:;]?\s)',
+               '**' => '(?<![\s*])\*\*(?!\*)',
+               '__' => '(?<![\s_])__(?![a-zA-Z0-9_])',
+       );
+       protected $em_strong_relist = array(
+               ''    => '(?:(?<!\*)\*\*\*(?!\*)|(?<![a-zA-Z0-9_])___(?!_))(?![\.,:;]?\s)',
+               '***' => '(?<![\s*])\*\*\*(?!\*)',
+               '___' => '(?<![\s_])___(?![a-zA-Z0-9_])',
+       );
+
+       /**
+        * Parse text into paragraphs
+        * @param  string $text String to process in paragraphs
+        * @param  boolean $wrap_in_p Whether paragraphs should be wrapped in <p> tags
+        * @return string       HTML output
+        */
+       protected function formParagraphs($text, $wrap_in_p = true) {
+               // Strip leading and trailing lines:
+               $text = preg_replace('/\A\n+|\n+\z/', '', $text);
+
+               $grafs = preg_split('/\n{2,}/', $text, -1, PREG_SPLIT_NO_EMPTY);
+
+               // Wrap <p> tags and unhashify HTML blocks
+               foreach ($grafs as $key => $value) {
+                       $value = trim($this->runSpanGamut($value));
+                       
+                       // Check if this should be enclosed in a paragraph.
+                       // Clean tag hashes & block tag hashes are left alone.
+                       $is_p = $wrap_in_p && !preg_match('/^B\x1A[0-9]+B|^C\x1A[0-9]+C$/', $value);
+                       
+                       if ($is_p) {
+                               $value = "<p>$value</p>";
+                       }
+                       $grafs[$key] = $value;
+               }
+               
+               // Join grafs in one text, then unhash HTML tags. 
+               $text = implode("\n\n", $grafs);
+               
+               // Finish by removing any tag hashes still present in $text.
+               $text = $this->unhash($text);
+               
+               return $text;
+       }
+       
+       
+       /**
+        * Footnotes - Strips link definitions from text, stores the URLs and
+        * titles in hash references.
+        * @param  string $text
+        * @return string
+        */
+       protected function stripFootnotes($text) {
+               $less_than_tab = $this->tab_width - 1;
+
+               // Link defs are in the form: [^id]: url "optional title"
+               $text = preg_replace_callback('{
+                       ^[ ]{0,' . $less_than_tab . '}\[\^(.+?)\][ ]?:  # note_id = $1
+                         [ ]*
+                         \n?                                   # maybe *one* newline
+                       (                                               # text = $2 (no blank lines allowed)
+                               (?:                                     
+                                       .+                              # actual text
+                               |
+                                       \n                              # newlines but 
+                                       (?!\[.+?\][ ]?:\s)# negative lookahead for footnote or link definition marker.
+                                       (?!\n+[ ]{0,3}\S)# ensure line is not blank and followed 
+                                                                       # by non-indented content
+                               )*
+                       )               
+                       }xm',
+                       array($this, '_stripFootnotes_callback'),
+                       $text);
+               return $text;
+       }
+
+       /**
+        * Callback for stripping footnotes
+        * @param  array $matches
+        * @return string
+        */
+       protected function _stripFootnotes_callback($matches) {
+               $note_id = $this->fn_id_prefix . $matches[1];
+               $this->footnotes[$note_id] = $this->outdent($matches[2]);
+               return ''; // String that will replace the block
+       }
+
+       /**
+        * Replace footnote references in $text [^id] with a special text-token 
+        * which will be replaced by the actual footnote marker in appendFootnotes.
+        * @param  string $text
+        * @return string
+        */
+       protected function doFootnotes($text) {
+               if (!$this->in_anchor) {
+                       $text = preg_replace('{\[\^(.+?)\]}', "F\x1Afn:\\1\x1A:", $text);
+               }
+               return $text;
+       }
+
+       /**
+        * Append footnote list to text
+        * @param  string $text
+        * @return string
+        */
+       protected function appendFootnotes($text) {
+               $text = preg_replace_callback('{F\x1Afn:(.*?)\x1A:}', 
+                       array($this, '_appendFootnotes_callback'), $text);
+       
+               if (!empty($this->footnotes_ordered)) {
+                       $text .= "\n\n";
+                       $text .= "<div class=\"footnotes\">\n";
+                       $text .= "<hr" . $this->empty_element_suffix . "\n";
+                       $text .= "<ol>\n\n";
+
+                       $attr = "";
+                       if ($this->fn_backlink_class != "") {
+                               $class = $this->fn_backlink_class;
+                               $class = $this->encodeAttribute($class);
+                               $attr .= " class=\"$class\"";
+                       }
+                       if ($this->fn_backlink_title != "") {
+                               $title = $this->fn_backlink_title;
+                               $title = $this->encodeAttribute($title);
+                               $attr .= " title=\"$title\"";
+                       }
+                       $backlink_text = $this->fn_backlink_html;
+                       $num = 0;
+                       
+                       while (!empty($this->footnotes_ordered)) {
+                               $footnote = reset($this->footnotes_ordered);
+                               $note_id = key($this->footnotes_ordered);
+                               unset($this->footnotes_ordered[$note_id]);
+                               $ref_count = $this->footnotes_ref_count[$note_id];
+                               unset($this->footnotes_ref_count[$note_id]);
+                               unset($this->footnotes[$note_id]);
+                               
+                               $footnote .= "\n"; // Need to append newline before parsing.
+                               $footnote = $this->runBlockGamut("$footnote\n");                                
+                               $footnote = preg_replace_callback('{F\x1Afn:(.*?)\x1A:}', 
+                                       array($this, '_appendFootnotes_callback'), $footnote);
+                               
+                               $attr = str_replace("%%", ++$num, $attr);
+                               $note_id = $this->encodeAttribute($note_id);
+
+                               // Prepare backlink, multiple backlinks if multiple references
+                               $backlink = "<a href=\"#fnref:$note_id\"$attr>$backlink_text</a>";
+                               for ($ref_num = 2; $ref_num <= $ref_count; ++$ref_num) {
+                                       $backlink .= " <a href=\"#fnref$ref_num:$note_id\"$attr>$backlink_text</a>";
+                               }
+                               // Add backlink to last paragraph; create new paragraph if needed.
+                               if (preg_match('{</p>$}', $footnote)) {
+                                       $footnote = substr($footnote, 0, -4) . "&#160;$backlink</p>";
+                               } else {
+                                       $footnote .= "\n\n<p>$backlink</p>";
+                               }
+                               
+                               $text .= "<li id=\"fn:$note_id\">\n";
+                               $text .= $footnote . "\n";
+                               $text .= "</li>\n\n";
+                       }
+                       
+                       $text .= "</ol>\n";
+                       $text .= "</div>";
+               }
+               return $text;
+       }
+
+       /**
+        * Callback for appending footnotes
+        * @param  array $matches
+        * @return string
+        */
+       protected function _appendFootnotes_callback($matches) {
+               $node_id = $this->fn_id_prefix . $matches[1];
+               
+               // Create footnote marker only if it has a corresponding footnote *and*
+               // the footnote hasn't been used by another marker.
+               if (isset($this->footnotes[$node_id])) {
+                       $num =& $this->footnotes_numbers[$node_id];
+                       if (!isset($num)) {
+                               // Transfer footnote content to the ordered list and give it its
+                               // number
+                               $this->footnotes_ordered[$node_id] = $this->footnotes[$node_id];
+                               $this->footnotes_ref_count[$node_id] = 1;
+                               $num = $this->footnote_counter++;
+                               $ref_count_mark = '';
+                       } else {
+                               $ref_count_mark = $this->footnotes_ref_count[$node_id] += 1;
+                       }
+
+                       $attr = "";
+                       if ($this->fn_link_class != "") {
+                               $class = $this->fn_link_class;
+                               $class = $this->encodeAttribute($class);
+                               $attr .= " class=\"$class\"";
+                       }
+                       if ($this->fn_link_title != "") {
+                               $title = $this->fn_link_title;
+                               $title = $this->encodeAttribute($title);
+                               $attr .= " title=\"$title\"";
+                       }
+                       
+                       $attr = str_replace("%%", $num, $attr);
+                       $node_id = $this->encodeAttribute($node_id);
+                       
+                       return
+                               "<sup id=\"fnref$ref_count_mark:$node_id\">".
+                               "<a href=\"#fn:$node_id\"$attr>$num</a>".
+                               "</sup>";
+               }
+               
+               return "[^" . $matches[1] . "]";
+       }
+               
+       
+       /**
+        * Abbreviations - strips abbreviations from text, stores titles in hash
+        * references.
+        * @param  string $text
+        * @return string
+        */
+       protected function stripAbbreviations($text) {
+               $less_than_tab = $this->tab_width - 1;
+
+               // Link defs are in the form: [id]*: url "optional title"
+               $text = preg_replace_callback('{
+                       ^[ ]{0,' . $less_than_tab . '}\*\[(.+?)\][ ]?:  # abbr_id = $1
+                       (.*)                                    # text = $2 (no blank lines allowed)    
+                       }xm',
+                       array($this, '_stripAbbreviations_callback'),
+                       $text);
+               return $text;
+       }
+
+       /**
+        * Callback for stripping abbreviations
+        * @param  array $matches
+        * @return string
+        */
+       protected function _stripAbbreviations_callback($matches) {
+               $abbr_word = $matches[1];
+               $abbr_desc = $matches[2];
+               if ($this->abbr_word_re) {
+                       $this->abbr_word_re .= '|';
+               }
+               $this->abbr_word_re .= preg_quote($abbr_word);
+               $this->abbr_desciptions[$abbr_word] = trim($abbr_desc);
+               return ''; // String that will replace the block
+       }
+
+       /**
+        * Find defined abbreviations in text and wrap them in <abbr> elements.
+        * @param  string $text
+        * @return string
+        */
+       protected function doAbbreviations($text) {
+               if ($this->abbr_word_re) {
+                       // cannot use the /x modifier because abbr_word_re may 
+                       // contain significant spaces:
+                       $text = preg_replace_callback('{' .
+                               '(?<![\w\x1A])' .
+                               '(?:' . $this->abbr_word_re . ')' .
+                               '(?![\w\x1A])' .
+                               '}',
+                               array($this, '_doAbbreviations_callback'), $text);
+               }
+               return $text;
+       }
+
+       /**
+        * Callback for processing abbreviations
+        * @param  array $matches
+        * @return string
+        */
+       protected function _doAbbreviations_callback($matches) {
+               $abbr = $matches[0];
+               if (isset($this->abbr_desciptions[$abbr])) {
+                       $desc = $this->abbr_desciptions[$abbr];
+                       if (empty($desc)) {
+                               return $this->hashPart("<abbr>$abbr</abbr>");
+                       } else {
+                               $desc = $this->encodeAttribute($desc);
+                               return $this->hashPart("<abbr title=\"$desc\">$abbr</abbr>");
+                       }
+               } else {
+                       return $matches[0];
+               }
+       }
+}