function &getDebugAsXMLComment()
    {
        // it would be nice to use a memory stream here to use
        // memory more efficiently
        while (strpos($this->debug_str, '--')) {
            $this->debug_str = str_replace('--', '- -', $this->debug_str);
        }
        $ret = "<!--\n" . $this->debug_str . "\n-->";

        return $ret;
    }