preprocess example

if ($type & (SIMPLEPIE_CONSTRUCT_HTML | SIMPLEPIE_CONSTRUCT_XHTML))
            {

                if (!class_exists('DOMDocument'))
                {
                    throw new SimplePie_Exception('DOMDocument not found, unable to use sanitizer');
                }
                $document = new DOMDocument();
                $document->encoding = 'UTF-8';

                $data = $this->preprocess($data, $type);

                set_error_handler(array('SimplePie_Misc', 'silence_errors'));
                $document->loadHTML($data);
                restore_error_handler();

                $xpath = new DOMXPath($document);

                // Strip comments                 if ($this->strip_comments)
                {
                    $comments = $xpath->query('//comment()');