emailObfuscate output modifier for MODx

emailObfuscate.php

<?php
/**
 * emailObfuscate output modifier for MODx
 * Version: 1.0.0
 *
 * based on ObfuscateEmail plugin 0.9.1 (Apr 15, 2007) by Aloysius Lim.
 * released under Public Domain.
 * http://modxcms.com/extras/package/?package=322
 *
 * This modifier searches for all email addresses and "mailto:" strings in the
 * input, both inside and outside href attributes. In other words, it also
 * encodes link text.
 *
 * It can find all common email addresses as specified by RFC2822, including all
 * unusual but allowed characters. Any email addresses that satisfy the
 * the construct below will be detected:
 *
 * The plugin than randomly leaves 10% of the characters alone, encodes 45% of
 * them in decimal, and 45% of them in hexadecimal.
 *
 * Output modifier example: [[*myTv:emailObfuscate]] or [[$myChunk:emailObfuscate]]
 *
 * Snippet example:
 *
 * [[emailObfuscate? 
 *   &input=`<a href="mailto:info@mydomain.com">info@mydomain.com</a>`
 * ]]
 * 
 * Changelog:
 * Version 1.0.0 (Feb 12, 2011) Enrique Erne
 * ported to MODx Revolution as output modifier
 *
 * Version 0.9.1 (Apr 15, 2007)
 * Fixed: Regex for atom allowed empty string.
 * 
 * Version 0.9.0 (Mar 16, 2007)
 * Original release.
 **/

if (!function_exists('email_regex')){
	function email_regex(){
		/* Set up email regex that partially conforms to RFC2822
		 * (the ignored parts are indicated):
		 * 
		 * addr-spec	= local-part "@" domain
		 * 
		 * local-part	= dot-atom
		 *			/ quoted-string	 // Ignored
		 *			/ obs-local-part // Ignored
		 * 
		 * domain	= dot-atom
		 *			/ domain-literal // Ignored
		 *			/ obs-domain	 // Ignored
		 *
		 * dot-atom	= [CFWS] dot-atom-text [CFWS] // Ignored CFWS
		 *
		 * dot-atom-text = 1*atext *("." 1*atext)
		 * atext	 = ALPHA / DIGIT / ; Any character except controls,
		 * "!" / "#" /		; SP, and specials.
		 * "$" / "%" /		; Used for atoms
		 * "&" / "'" /
		 * "*" / "+" /
		 * "-" / "/" /
		 * "=" / "?" /
		 * "^" / "_" /
		 * "`" / "{" /
		 * "|" / "}" /
		 * "~"
		 */
		
		$atom = "[-!#$%&'*+/=?^_`{|}~0-9A-Za-z]+";
		$email_half = $atom . '(?:\\.' . $atom . ')*';
		$email = $email_half . '@' . $email_half;
		$email_regex = '<(' . $email . ')>';
		return $email_regex;
	}
}

if (!function_exists('replaceEntities')){
	function replaceEntities($matches){
		$address = html_entity_decode($matches[1]);
		$replaced = '';
		
		for ($i = 0 ; $i < strlen($address) ; $i++){
			$char = $address[$i];
			$r = rand(0, 100);

			# roughly 10% raw, 45% hex, 45% dec
			if ($r > 90){
				$replaced .= $char;
			} else if ($r < 45){
				$replaced .= '&#x' . dechex(ord($char)) . ';';
			} else {
				$replaced .= '&#' . ord($char) . ';';
			}
		}
		return $replaced;
	}
}

$output = preg_replace_callback(email_regex(), 'replaceEntities', $input);
return preg_replace_callback('/(mailto:)/', 'replaceEntities', $output);