private static function _getTreeElm($str, &$info)
    {
        /*
         * Normalize the string.
         */
        $str = preg_replace('/(\n\r|\n|\r|\s)+/', ' ', $str);

        /*
         * Identify it by checking its first symbols.
         */
        if (strpos($str, '</') === 0) {
            return 'end';
        } elseif (strpos($str, '<!') === 0) {
            return 'content';
        } elseif (strpos($str, '<!--') === 0) {
            return 'comment';
        } elseif (strpos($str, '<') === 0) {
            preg_match('/<([a-zA-Z0-9]+)(.*?(?=\/>|>))(\/>|>)+/', $str, $info);

            return 'start';
        }

        return 'content';
    }