filter.php

<?PHP // $Id$
      // This class looks for email addresses in Moodle text and 
      // hides them using the Moodle obfuscate_text function. 
      // Original code by Mike Churchward

class emailprotect_filter extends filter_base {
    function __construct($courseid, $format, $options) {
        parent::__construct($courseid, $format, $options);
    }
    function filter($text) {
        if (!empty($CFG->formatstring)) {
            return $text;
        }
                                                
    /// Do a quick check using stripos to avoid unnecessary work
        if (strpos($text, '@') === false) {
            return $text;
        }

    /// There might be an email in here somewhere so continue ...
        $matches = array();

    /// regular expression to define a standard email string.
        $emailregex = '((?:[\w\.\-])+\@(?:(?:[a-zA-Z\d\-])+\.)+(?:[a-zA-Z\d]{2,4}))';

    /// pattern to find a mailto link with the linked text.
        $pattern = '|(<a\s+href\s*=\s*[\'"]?mailto:)'.$emailregex.'([\'"]?\s*>)'.'(.*)'.'(</a>)|iU';
        $text = preg_replace_callback($pattern, 'alter_mailto', $text);

    /// pattern to find any other email address in the text.
        $pattern = '/(^|\s+|>)'.$emailregex.'($|\s+|\.\s+|\.$|<)/i';
        $text = preg_replace_callback($pattern, 'alter_email', $text);

        return $text;
    }
}

function alter_email($matches) {
    return $matches[1].obfuscate_text($matches[2]).$matches[3];
}

function alter_mailto($matches) {
    return obfuscate_mailto($matches[2], $matches[4]);
}

?>