protected function parseUrl($url)
    {
        // The regular expression is copied verbatim from RFC 3986, appendix B.
        // The expression does not validate the URL but matches any string.
        preg_match(
            '(^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?)',
            $url, $matches
        );

        // "path" is always present (possibly as an empty string); the rest
        // are optional.
        $this->_scheme   = !empty($matches[1]) ? $matches[2] : false;
        $this->setAuthority(!empty($matches[3]) ? $matches[4] : false);
        $this->_path     = $this->_encodeData($matches[5]);
        $this->_query    = !empty($matches[6])
                           ? $this->_encodeData($matches[7])
                           : false
            ;
        $this->_fragment = !empty($matches[8]) ? $matches[9] : false;
    }