public function url() {
        // TODO: class for url
        if ($this->url === null) {
            $this->url = parse_url(
                'http' .
                (isset($serverVariables['HTTPS']) ? 's' : '') .
                '://' .
                $serverVariables['HTTP_HOST'] .
                $serverVariables['REQUEST_URI']
            );
        }

        return $this->url;
    }