PayPal\Ipn\PPIPNMessage::getTransactionId PHP Method

    public function getTransactionId()
    {
        if (isset($this->ipnData['txn_id'])) {
            return $this->ipnData['txn_id'];
        } else {
            if (isset($this->ipnData['transaction[0].id'])) {
                $idx = 0;
                do {
                    $transId[] = $this->ipnData["transaction[{$idx}].id"];
                    $idx++;
                } while (isset($this->ipnData["transaction[{$idx}].id"]));
                return $transId;
            }
        }
    }

 /**
  * @Route ("/ipn")
  * @Transactional
  *
  * Handles the incoming HTTP request
  * @param array $params
  */
 public function ipn(array $params)
 {
     $log = Application::instance()->getLogger();
     try {
         $ipnMessage = new PPIPNMessage();
         if (!$ipnMessage->validate()) {
             $log->error('Got a invalid IPN ' . json_encode($ipnMessage->getRawData()));
             return new Response(Http::STATUS_ERROR, 'Got a invalid IPN');
         }
         $data = $ipnMessage->getRawData();
         $log->info(sprintf('Got a valid IPN [txn_id: %s, txn_type: %s]', $ipnMessage->getTransactionId(), $data['txn_type']));
         $orderService = OrdersService::instance();
         $orderService->addIPNRecord(array('ipnTrackId' => $data['ipn_track_id'], 'ipnTransactionId' => $data['txn_id'], 'ipnTransactionType' => $data['txn_type'], 'ipnData' => json_encode($data, JSON_UNESCAPED_UNICODE)));
         // Make sure this IPN is for the merchant
         if (strcasecmp(Config::$a['commerce']['receiver_email'], $data['receiver_email']) !== 0) {
             $log->critical(sprintf('IPN originated with incorrect receiver_email [%s]', $data['ipn_track_id']));
             return new Response(Http::STATUS_ERROR, 'Invalid IPN');
         }
         // Handle the IPN
         $this->handleIPNTransaction($data['txn_id'], $data['txn_type'], $data);
         // Return success response
         return new Response(Http::STATUS_OK);
     } catch (\Exception $e) {
         $log->critical($e->getMessage());
         return new Response(Http::STATUS_ERROR, 'Error');
     }
     $log->critical('Unhandled IPN');
     return new Response(Http::STATUS_ERROR, 'Unhandled IPN');
 }