public function url(string $url = null) : self
    {
        if (! $url) {
            $url = null;

            $httpHost = getenv('APP_URL'); // Has to start with a protocol - for example "http://"!

            if ($httpHost === false) {
                $url = 'http';

                // Quick and dirty
                if (isset($_SERVER['HTTPS'])) {
                    $url .= 's';
                }

                $url .= '://';

                $httpHost = isset($_SERVER['HTTP_HOST']) ? $_SERVER['HTTP_HOST'] : 'localhost/';
            }  

            $requestUri = isset($_SERVER['REQUEST_URI']) ? $_SERVER['REQUEST_URI'] : '';
            
            $safeRequestURI = htmlentities(strip_tags(urldecode($requestUri)));

            $url .= "{$httpHost}{$safeRequestURI}";
        } 

        if ($this->validate and ! filter_var($url, FILTER_VALIDATE_URL)) {
            throw new Exception("Open Graph: Invalid URL '{$url}'");
        }

        $this->forget('url');

        $this->tags[] = $this->createTag('url', $url);

        return $this;
    }