OneLogin_Saml2_Response::_queryAssertion PHP Method

    protected function _queryAssertion($assertionXpath)
    {
        if ($this->encrypted) {
            $xpath = new DOMXPath($this->decryptedDocument);
        } else {
            $xpath = new DOMXPath($this->document);
        }
        $xpath->registerNamespace('samlp', OneLogin_Saml2_Constants::NS_SAMLP);
        $xpath->registerNamespace('saml', OneLogin_Saml2_Constants::NS_SAML);
        $xpath->registerNamespace('ds', OneLogin_Saml2_Constants::NS_DS);
        $xpath->registerNamespace('xenc', OneLogin_Saml2_Constants::NS_XENC);
        $assertionNode = '/samlp:Response/saml:Assertion';
        $signatureQuery = $assertionNode . '/ds:Signature/ds:SignedInfo/ds:Reference';
        $assertionReferenceNode = $xpath->query($signatureQuery)->item(0);
        if (!$assertionReferenceNode) {
            // is the response signed as a whole?
            $signatureQuery = '/samlp:Response/ds:Signature/ds:SignedInfo/ds:Reference';
            $responseReferenceNode = $xpath->query($signatureQuery)->item(0);
            if ($responseReferenceNode) {
                $uri = $responseReferenceNode->attributes->getNamedItem('URI')->nodeValue;
                if (empty($uri)) {
                    $id = $responseReferenceNode->parentNode->parentNode->parentNode->attributes->getNamedItem('ID')->nodeValue;
                } else {
                    $id = substr($responseReferenceNode->attributes->getNamedItem('URI')->nodeValue, 1);
                }
                $nameQuery = "/samlp:Response[@ID='{$id}']/saml:Assertion" . $assertionXpath;
            } else {
                $nameQuery = "/samlp:Response/saml:Assertion" . $assertionXpath;
            }
        } else {
            $uri = $assertionReferenceNode->attributes->getNamedItem('URI')->nodeValue;
            if (empty($uri)) {
                $id = $assertionReferenceNode->parentNode->parentNode->parentNode->attributes->getNamedItem('ID')->nodeValue;
            } else {
                $id = substr($assertionReferenceNode->attributes->getNamedItem('URI')->nodeValue, 1);
            }
            $nameQuery = $assertionNode . "[@ID='{$id}']" . $assertionXpath;
        }
        return $xpath->query($nameQuery);
    }