private static function getProxyConfiguration($url)
    {
        $hostname = UrlHelper::getHostFromUrl($url);

        if (Url::isLocalHost($hostname)) {
            return array(null, null, null, null);
        }

        // proxy configuration
        $proxyHost = Config::getInstance()->proxy['host'];
        $proxyPort = Config::getInstance()->proxy['port'];
        $proxyUser = Config::getInstance()->proxy['username'];
        $proxyPassword = Config::getInstance()->proxy['password'];

        return array($proxyHost, $proxyPort, $proxyUser, $proxyPassword);
    }