<?phprequire_once 'HTMLPurifier/Filter.php';class HTMLPurifier_Filter_YouTube extends HTMLPurifier_Filter{        var $name = 'YouTube preservation';        function preFilter($html, $config, &$context) {        $pre_regex = '#<object[^>]+>.+?'.            'http://www.youtube.com/v/([A-Za-z0-9\-_]+).+?</object>#s';        $pre_replace = '<span class="youtube-embed">\1</span>';        return preg_replace($pre_regex, $pre_replace, $html);    }        function postFilter($html, $config, &$context) {        $post_regex = '#<span class="youtube-embed">([A-Za-z0-9\-_]+)</span>#';        $post_replace = '<object width="425" height="350" '.            'data="http://www.youtube.com/v/\1">'.            '<param name="movie" value="http://www.youtube.com/v/\1"></param>'.            '<param name="wmode" value="transparent"></param>'.            '<!--[if IE]>'.            '<embed src="http://www.youtube.com/v/\1"'.            'type="application/x-shockwave-flash"'.            'wmode="transparent" width="425" height="350" />'.            '<![endif]-->'.            '</object>';        return preg_replace($post_regex, $post_replace, $html);    }    }