protected function getFederatedAuthenticationInformation($response) {
        if ($response) {
            $xml = new \DOMDocument();
            $xml->loadXML($response);
            $xpath = new \DOMXPath($xml);
            if ($xpath->query("//STSAuthURL")->length > 0) {
                return $xpath->query("//STSAuthURL")->item(0);
            }
        }
        return '';
    }