3 namespace Drupal\Component\Utility;
6 * Provides helpers to ensure emails are compliant with RFCs.
13 * RFC-2822 "specials" characters.
15 const RFC_2822_SPECIALS = '()<>[]:;@\,."';
18 * Return a RFC-2822 compliant "display-name" component.
20 * The "display-name" component is used in mail header "Originator" fields
21 * (From, Sender, Reply-to) to give a human-friendly description of the
22 * address, i.e. From: My Display Name <xyz@example.org>. RFC-822 and
23 * RFC-2822 define its syntax and rules. This method gets as input a string
24 * to be used as "display-name" and formats it to be RFC compliant.
26 * @param string $string
27 * A string to be used as "display-name".
30 * A RFC compliant version of the string, ready to be used as
31 * "display-name" in mail originator header fields.
33 public static function formatDisplayName($string) {
34 // Make sure we don't process html-encoded characters. They may create
35 // unneeded trouble if left encoded, besides they will be correctly
36 // processed if decoded.
37 $string = Html::decodeEntities($string);
39 // If string contains non-ASCII characters it must be (short) encoded
40 // according to RFC-2047. The output of a "B" (Base64) encoded-word is
41 // always safe to be used as display-name.
42 $safe_display_name = Unicode::mimeHeaderEncode($string, TRUE);
44 // Encoded-words are always safe to be used as display-name because don't
45 // contain any RFC 2822 "specials" characters. However
46 // Unicode::mimeHeaderEncode() encodes a string only if it contains any
47 // non-ASCII characters, and leaves its value untouched (un-encoded) if
48 // ASCII only. For this reason in order to produce a valid display-name we
49 // still need to make sure there are no "specials" characters left.
50 if (preg_match('/[' . preg_quote(Mail::RFC_2822_SPECIALS) . ']/', $safe_display_name)) {
52 // If string is already quoted, it may or may not be escaped properly, so
53 // don't trust it and reset.
54 if (preg_match('/^"(.+)"$/', $safe_display_name, $matches)) {
55 $safe_display_name = str_replace(['\\\\', '\\"'], ['\\', '"'], $matches[1]);
58 // Transform the string in a RFC-2822 "quoted-string" by wrapping it in
59 // double-quotes. Also make sure '"' and '\' occurrences are escaped.
60 $safe_display_name = '"' . str_replace(['\\', '"'], ['\\\\', '\\"'], $safe_display_name) . '"';
64 return $safe_display_name;