XMLSecurityDSig::canonicalizeSignedInfo PHP Method

    public function canonicalizeSignedInfo()
    {
        $doc = $this->sigNode->ownerDocument;
        $canonicalmethod = null;
        if ($doc) {
            $xpath = $this->getXPathObj();
            $query = "./secdsig:SignedInfo";
            $nodeset = $xpath->query($query, $this->sigNode);
            if ($signInfoNode = $nodeset->item(0)) {
                $query = "./secdsig:CanonicalizationMethod";
                $nodeset = $xpath->query($query, $signInfoNode);
                if ($canonNode = $nodeset->item(0)) {
                    $canonicalmethod = $canonNode->getAttribute('Algorithm');
                }
                $this->signedInfo = $this->canonicalizeData($signInfoNode, $canonicalmethod);
                return $this->signedInfo;
            }
        }
        return null;
    }

 /**
  * @return bool
  * @throws Exception
  */
 public function isValid()
 {
     $singleAssertion = $this->validateNumAssertions();
     if (!$singleAssertion) {
         throw new Exception('Multiple assertions are not supported');
     }
     $validTimestamps = $this->validateTimestamps();
     if (!$validTimestamps) {
         throw new Exception('Timing issues (please check your clock settings)');
     }
     $objXMLSecDSig = new XMLSecurityDSig();
     $objDSig = $objXMLSecDSig->locateSignature($this->_document);
     if (!$objDSig) {
         throw new Exception('Cannot locate Signature Node');
     }
     $objXMLSecDSig->canonicalizeSignedInfo();
     $objXMLSecDSig->idKeys = array('ID');
     $objKey = $objXMLSecDSig->locateKey();
     if (!$objKey) {
         throw new Exception('We have no idea about the key');
     }
     try {
         $retVal = $objXMLSecDSig->validateReference();
     } catch (Exception $e) {
         throw new Exception('Reference Validation Failed');
     }
     XMLSecEnc::staticLocateKeyInfo($objKey, $objDSig);
     $objKey->loadKey($this->_settings->idpPublicCertificate, false, true);
     return $objXMLSecDSig->verify($objKey) === 1;
 }