Paypal IPN keeps retrying and then it fails - php

Question

I've tested on IPN simulator and it seems fine, IPN is being sent and verified. Now I'm testing on sandbox, but in IPN History I can see that the delivery status keeps retrying and then it fails. It's never being sent. The HTTP response code field is empty. I'm working on localhost, but I'm using with ngrok where I receive the 200 OK HTTP response. I also want to insert data into mysql database, but I suppose it's also one of the reasons I can't. What am I doing wrong? I'm fairly new to PHP and I've gone through similar questions, but didn't seem to find a solution. I've been on this all day and it's driving me crazy. :) Any help or guideline would be much appreciated!
I'm using a script from github, here is the ipn.php:
<?php
include 'xxxxxxx.php';
require('PaypalIPN.php');
use PaypalIPN;
$ipn = new PayPalIPN();
// Use the sandbox endpoint during testing.
$ipn->useSandbox();
$verified = $ipn->verifyIPN();
if ($verified) {
$item_number = $_POST['item_number'];
$txn_id = $_POST['txn_id'];
$payment_gross = $_POST['mc_gross'];
$currency_code = $_POST['mc_currency'];
$payment_status = $_POST['payment_status'];
$insert =mysqli_query($conn, "INSERT INTO payments(item_number, txn_id,payment_gross,currency_code,payment_status) VALUES('".$item_number."','".$txn_id."','".$payment_gross."','".$currency_code."','".$payment_status."')");
}
?>
And here is my paypalIPN.php:
<?php
class PaypalIPN
{
private $use_sandbox = false;
private $use_local_certs = false;
/*
* PayPal IPN postback endpoints
*/
const VERIFY_URI = 'https://ipnpb.paypal.com/cgi-bin/webscr';
const SANDBOX_VERIFY_URI = 'https://ipnpb.sandbox.paypal.com/cgi-bin/webscr';
/*
* Possible responses from PayPal after the request is issued.
*/
const VALID = 'VERIFIED';
const INVALID = 'INVALID';
/**
* Sets the IPN verification to sandbox mode (for use when testing,
* should not be enabled in production).
* #return void
*/
public function useSandbox()
{
$this->use_sandbox = true;
}
/**
* Determine endpoint to post the verification data to.
* #return string
*/
public function getPaypalUri()
{
if ($this->use_sandbox) {
return self::SANDBOX_VERIFY_URI;
} else {
return self::VERIFY_URI;
}
}
/**
* Verification Function
* Sends the incoming post data back to paypal using the cURL library.
*
* #return bool
* #throws Exception
*/
public function verifyIPN()
{
if ( ! count($_POST)) {
throw new Exception("Missing POST Data");
}
$raw_post_data = file_get_contents('php://input');
$raw_post_array = explode('&', $raw_post_data);
$myPost = [];
foreach ($raw_post_array as $keyval) {
$keyval = explode('=', $keyval);
if (count($keyval) == 2) {
// Since we do not want the plus in the datetime string to be encoded to a space, we manually encode it.
if ($keyval[0] === 'payment_date') {
if (substr_count($keyval[1], '+') === 1) {
$keyval[1] = str_replace('+', '%2B', $keyval[1]);
}
}
$myPost[$keyval[0]] = urldecode($keyval[1]);
}
}
// Build the body of the verification post request, adding the _notify-validate command.
$req = 'cmd=_notify-validate';
$get_magic_quotes_exists = false;
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 the data back to paypal, using curl. Throw exceptions if errors occur.
$ch = curl_init($this->getPaypalUri());
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_SSLVERSION, 6);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 1);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
// This is often required if the server is missing a global cert bundle, or is using an outdated one.
if ($this->use_local_certs) {
curl_setopt($ch, CURLOPT_CAINFO, __DIR__ . "/cert/cacert.pem");
}
curl_setopt($ch, CURLOPT_FORBID_REUSE, 1);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 30);
curl_setopt($ch, CURLOPT_HTTPHEADER, ['Connection: Close']);
$res = curl_exec($ch);
$info = curl_getinfo($ch);
$http_code = $info['http_code'];
if ($http_code != 200) {
throw new Exception("PayPal responded with http code $http_code");
}
if ( ! ($res)) {
$errno = curl_errno($ch);
$errstr = curl_error($ch);
curl_close($ch);
throw new Exception("cURL error: [$errno] $errstr");
}
curl_close($ch);
// Check if paypal verfifes the IPN data, and if so, return true.
if ($res == self::VALID) {
return true;
} else {
return false;
}
}
}
I've also inserted the notify_url in my html form:
<input type='hidden' name='notify_url' value='http://xxxxxxx/xxxx/ipn.php'>