Paypal ipn (notify) no response in cakephp3

hello world,

there a link about Paypal tutorial, i have some error in the notify IPN side, which has no response of data sending back although it’s has a successful payment in sandbox mode.

the following is the code in php format

			          <?php
			// CONFIG: Enable debug mode. This means we'll log requests into 'ipn.log' in the 
                           same directory.
			// Especially useful if you encounter network errors or other intermittent problems 
                        with IPN (validation).
			// Set this to 0 once you go live or don't require logging.
			define("DEBUG", 1);
			// Set to 0 once you're ready to go live
			define("USE_SANDBOX", 1);
			define("LOG_FILE", "ipn.log");
			// Read POST data
			// reading posted data directly from $_POST causes serialization
			// issues with array data in POST. Reading raw POST data from input stream 
                           instead.
			$raw_post_data = file_get_contents('php://input');
			$raw_post_array = explode('&', $raw_post_data);
			$myPost = array();
			foreach ($raw_post_array as $keyval) {
				$keyval = explode ('=', $keyval);
				if (count($keyval) == 2)
					$myPost[$keyval[0]] = urldecode($keyval[1]);
			}
			// read the post from PayPal system and add 'cmd'
			$req = 'cmd=_notify-validate';
			if(function_exists('get_magic_quotes_gpc')) {
				$get_magic_quotes_exists = true;
			}
			foreach ($myPost as $key => $value) {
				if($get_magic_quotes_exists == true && get_magic_quotes_gpc() == 1) {
					$value = urlencode(stripslashes($value));
				} else {
					$value = urlencode($value);
				}
				$req .= "&$key=$value";
			}
			// Post IPN data back to PayPal to validate the IPN data is genuine
			// Without this step anyone can fake IPN data
			if(USE_SANDBOX == true) {
				$paypal_url = "https://www.sandbox.paypal.com/cgi-bin/webscr";
			} else {
				$paypal_url = "https://www.paypal.com/cgi-bin/webscr";
			}
			$ch = curl_init($paypal_url);
			if ($ch == FALSE) {
				return FALSE;
			}
			curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1);
			curl_setopt($ch, CURLOPT_POST, 1);
			curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
			curl_setopt($ch, CURLOPT_POSTFIELDS, $req);
			curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 1);
			curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
			curl_setopt($ch, CURLOPT_FORBID_REUSE, 1);
			if(DEBUG == true) {
				curl_setopt($ch, CURLOPT_HEADER, 1);
				curl_setopt($ch, CURLINFO_HEADER_OUT, 1);
			}
			// CONFIG: Optional proxy configuration
			//curl_setopt($ch, CURLOPT_PROXY, $proxy);
			//curl_setopt($ch, CURLOPT_HTTPPROXYTUNNEL, 1);
			// Set TCP timeout to 30 seconds
			curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 30);
			curl_setopt($ch, CURLOPT_HTTPHEADER, array('Connection: Close'));
			// CONFIG: Please download 'cacert.pem' from 
                             "http://curl.haxx.se/docs/caextract.html" and set the directory path
			// of the certificate as shown below. Ensure the file is readable by the webserver.
			// This is mandatory for some environments.
			//$cert = __DIR__ . "./cacert.pem";
			//curl_setopt($ch, CURLOPT_CAINFO, $cert);
			$res = curl_exec($ch);
			if (curl_errno($ch) != 0) // cURL error
				{
				if(DEBUG == true) {	
					error_log(date('[Y-m-d H:i e] '). "Can't connect to PayPal to validate IPN 
                             message: " . curl_error($ch) . PHP_EOL, 3, LOG_FILE);
				}
				curl_close($ch);
				exit;
			} else {
					// Log the entire HTTP response if debug is switched on.
					if(DEBUG == true) {
						error_log(date('[Y-m-d H:i e] '). "HTTP request of validation 
                          request:". curl_getinfo($ch, CURLINFO_HEADER_OUT) ." for IPN payload: $req" . 
                         PHP_EOL, 3, LOG_FILE);
						error_log(date('[Y-m-d H:i e] '). "HTTP response of validation 
                          request: $res" . PHP_EOL, 3, LOG_FILE);
					}
					curl_close($ch);
			}
			// Inspect IPN validation result and act accordingly
			// Split response headers and payload, a better way for strcmp
			$tokens = explode("\r\n\r\n", trim($res));
			$res = trim(end($tokens));
			if (strcmp ($res, "VERIFIED") == 0) {
				// assign posted variables to local variables
				$item_name = $_POST['item_name'];
				$item_number = $_POST['item_number'];
				$payment_status = $_POST['payment_status'];
				$payment_amount = $_POST['mc_gross'];
				$payment_currency = $_POST['mc_currency'];
				$txn_id = $_POST['txn_id'];
				$receiver_email = $_POST['receiver_email'];
				$payer_email = $_POST['payer_email'];
				
				include("DBController.php");
				$db = new DBController();
				
				// check whether the payment_status is Completed
				$isPaymentCompleted = false;
				if($payment_status == "Completed") {
					$isPaymentCompleted = true;
				}
				// check that txn_id has not been previously processed
				$isUniqueTxnId = false; 
				$param_type="s";
				$param_value_array = array($txn_id);
				$result = $db->runQuery("SELECT * FROM payment WHERE txn_id = 
                                  ?",$param_type,$param_value_array);
				if(empty($result)) {
			        $isUniqueTxnId = true;
				}	
				// check that receiver_email is your PayPal email
				// check that payment_amount/payment_currency are correct
				if($isPaymentCompleted) {
				    $param_type = "sssdss";
				    $param_value_array = array($item_number, $item_name, 
                                       $payment_status, $payment_amount, $payment_currency, $txn_id);
				    $payment_id = $db->insert("INSERT INTO payment(item_number, 
                                      item_name, payment_status, payment_amount, payment_currency, txn_id) 
                                     VALUES(?, ?, ?, ?, ?, ?)", $param_type, $param_value_array);
				    
				} 
				// process payment and mark item as paid.
				
				
				if(DEBUG == true) {
					error_log(date('[Y-m-d H:i e] '). "Verified IPN: $req ". PHP_EOL, 3, 
                            LOG_FILE);
				}
				
			} else if (strcmp ($res, "INVALID") == 0) {
				// log for manual investigation
				// Add business logic here which deals with invalid IPN messages
				if(DEBUG == true) {
					error_log(date('[Y-m-d H:i e] '). "Invalid IPN: $req" . PHP_EOL, 3, 
                          LOG_FILE);
				}
			}
			?>

the above code comes from link PayPal Payment Gateway Integration in PHP - Phppot

i modified the above codes into Payments Controller in notify function, the codes as follows:-

             public function notify()
              {
          
          
          
          
                  // Read POST data
                  // reading posted data directly from $_POST causes serialization
                  // issues with array data in POST. Reading raw POST data from input stream instead.
                  $request = new ServerRequest();
                  $raw_post_data = $request->getBody()->getContents();
                  $raw_post_array = explode('&', $raw_post_data);
                  $myPost = [];
                  foreach ($raw_post_array as $keyval) {
                      $keyval = explode('=', $keyval);
                      if (count($keyval) == 2) {
                          $myPost[$keyval[0]] = urldecode($keyval[1]);
                      }
                  }
          
          
              
          
          
                  // read the post from PayPal system and add 'cmd'
                  $req = 'cmd=_notify-validate';
          
                  if (function_exists('get_magic_quotes_gpc') && ini_get('magic_quotes_gpc')  == 1) {
                      $get_magic_quotes_exists = true;
                  } else {
                      $get_magic_quotes_exists = false;
                  }
          
                  foreach ($myPost as $key => $value) {
                      if ($get_magic_quotes_exists) {
                          $value = urlencode(stripslashes($value));
                      } else {
                          $value = urlencode($value);
                      }
          
                      $req .= "&$key=$value";
                  }
          
          
          
                  $DEBUG = true;
                  $USE_SANDBOX = true;
                  $LOG_FILE = 'ipn.log';
          
                  // your controller actions and methods go here
                  $SANDBOX_URL = 'https://www.sandbox.paypal.com/cgi-bin/webscr';
                  $PRODUCTION_URL = 'https://www.paypal.com/cgi-bin/webscr';
          
          
                  // Post IPN data back to PayPal to validate the IPN data is genuine
                  // Without this step anyone can fake IPN data
                  if ($USE_SANDBOX == true) {
                      $paypal_url = "https://www.sandbox.paypal.com/cgi-bin/webscr";
                  } else {
                      $paypal_url = "https://www.paypal.com/cgi-bin/webscr";
                  }
          
                  $client = new Client();
                  $response = $client->post($paypal_url, $req, [
                      'httpversion' => CURL_HTTP_VERSION_1_1,
                      'ssl_verify_peer' => true,
                      'ssl_verify_host' => 2,
                      'forbid_reuse' => true,
                      'connecttimeout' => 30,
                      'headers' => [
                          'Connection' => 'Close'
                      ]
                  ]);
          
                  if ($response->isOk()) {
                      $res = $response->getBody();
                      // Log the entire HTTP response if debug is switched on.
                      if ($DEBUG == true) {
                          error_log(date('[Y-m-d H:i e] ') . "HTTP request of validation request:" . $response->$this->request()->getHeadersAsString() . " for IPN payload: $req" . PHP_EOL, 3,  $LOG_FILE);
                          error_log(date('[Y-m-d H:i e] ') . "HTTP response of validation request: $res" . PHP_EOL, 3,  $LOG_FILE);
                      }
                  } else {
                      if ($DEBUG == true) {
                          error_log(date('[Y-m-d H:i e] ') . "Can't connect to PayPal to validate IPN message: " . $response->getReasonPhrase() . PHP_EOL, 3,  $LOG_FILE);
                      }
                      exit;
                  }
          
          
          
                  // Inspect IPN validation result and act accordingly
                  // Split response headers and payload, a better way for strcmp
                  $tokens = explode("\r\n\r\n", trim($res));
                  $res = trim(end($tokens));
                  if (strcmp($res, "VERIFIED") == 0) {
                      // assign posted variables to local variables
                      $item_name = $this->request->getData('item_name');
                      $item_number = $this->request->getData('item_number');
                      $payment_status = $this->request->getData('payment_status');
                      $payment_amount = $this->request->getData('mc_gross');
                      $payment_currency = $this->request->getData('mc_currency');
                      $txn_id = $this->request->getData('txn_id');
                      $receiver_email = $this->request->getData('receiver_email');
                      $payer_email = $this->request->getData('payer_email');
          
                     
                      // check whether the payment_status is Completed
                      $isPaymentCompleted = false;
                      if ($payment_status == "Completed") {
                          $isPaymentCompleted = true;
                      }
          
                      // check that txn_id has not been previously processed
                      // $isUniqueTxnId = false;
                      // $payment = $this->Payments->find()->where(['txn_id' => $txn_id])->first();
                      // if (empty($payment)) {
                      //     $isUniqueTxnId = true;
                      // }
          
                      // check that receiver_email is your PayPal email
                      // check that payment_amount/payment_currency are correct
                      if ($isPaymentCompleted) {
          
                          $payment = $this->Payments->newEntity();
          
                          $payment = $this->Payments->patchEntity($payment, $this->request->getData());
                         
                              $payment['item_name'] = $this->request->getData('item_name');
                              $payment['item_number'] = $this->request->getData('item_number');
                              $payment['payment_status'] = $this->request->getData('payment_status');
                              $payment['payment_amount'] = $this->request->getData('mc_gross');
                              $payment['payment_currency'] = $this->request->getData('mc_currency');
                              $payment['txn_id'] = $this->request->getData('txn_id');
                             
                      
                          $this->Payments->save($payment);
                          error_log(date('[Y-m-d H:i e] ') . "Verified IPN: $req " . PHP_EOL, 3, $LOG_FILE);
                      }
          
                      // process payment and mark item as paid.
          
                      if ($DEBUG == true) {
                          error_log(date('[Y-m-d H:i e] ') . "Verified IPN: $req " . PHP_EOL, 3, $LOG_FILE);
                      }
                  } else if (strcmp($res, "INVALID") == 0) {
                      // log for manual investigation
                      // Add business logic here which deals with invalid IPN messages
                      if ($DEBUG == true) {
                          error_log(date('[Y-m-d H:i e] ') . "Invalid IPN: $req" . PHP_EOL, 3, $LOG_FILE);
                      }
                  }
              }

this notify seemed no response and not saving data to Payments table.

how can i modify the codes to rectify it?

thanks