code: public function createResponse($status, $errorCode, $errorDescription)
      {
          $document = new \DOMDocument('1.0', 'utf-8');
          $document->formatOutput = false;
  
          $response = $document->appendChild(
              $document->createElement('SVSPurchaseStatusNotificationResponse')
          );
  
          $result = $response->appendChild(
              $document->createElement('TransactionResult')
          );
  
          $result->appendChild(
              $document->createElement('Description', $errorDescription)
          );
  
          $result->appendChild(
              $document->createElement('Code', $errorCode)
          );
  
          $response->appendChild(
              $document->createElement('Status', $status)
          );
  
          $authentication = $response->appendChild(
              $document->createElement('Authentication')
          );
  
          $checksum = $authentication->appendChild(
              $document->createElement('Checksum', $this->getMerchantPassword())
          );
  
          $checksum->nodeValue = $this->calculateXmlChecksum($document->saveXML());
  
          return $document->saveXML();
      }
docs: Respond to Ecopayz confirming or rejecting the payment.
  
  One of the following status codes:
  - InvalidRequest
  - OK
  - Confirmed
  - Cancelled
  
  @param  string $status           The ecopayz status code
  @param  int    $errorCode        The merchant error code
  @param  string $errorDescription The merchant error description
  @return string response