PayPal Payment Verification, How the IPN works - php

Question

I am searching for how to use the PayPal IPN (Instant Payment Notification) from past 2 weeks and couldn't understand how exactly to use it in my code.
I am using the following HTML code to create a PayPal button
button.html
<form name="paypalForm" action="paypal.php" method="post">
<input type="hidden" name="id" value="123">
<input type="hidden" name="CatDescription" value="20Percents (12 Credits)">
<input type="hidden" name="payment" value="10">
<input type="hidden" name="key" value="<? echo md5(date("Y-m-d:").rand()); ?>">
<input TYPE="image" SRC="http://www.coachsbr.com/images/site/paypal_button.gif" name="paypal" value="Payment via Paypal" >
</form>
And, the following code to process the payment and verify it
paypal.php
<?php
require_once('paypal.class.php'); // include the class file
$p = new paypal_class; // initiate an instance of the class
$p->paypal_url = 'https://www.sandbox.paypal.com/cgi-bin/webscr'; // testing paypal url
//$p->paypal_url = 'https://www.paypal.com/cgi-bin/webscr'; // paypal url
// setup a variable for this script (ie: 'http://www.micahcarrick.com/paypal.php')
$this_script = 'http://'.$_SERVER['HTTP_HOST'].$_SERVER['PHP_SELF'];
// if there is not action variable, set the default action of 'process'
if (empty($_GET['action'])) $_GET['action'] = 'process';
switch ($_GET['action']) {
case 'process': // Process and order...
$CatDescription = $_REQUEST['CatDescription'];
$payment = $_REQUEST['payment'];
$id = $_REQUEST['id'];
$key = $_REQUEST['key'];
$p->add_field('business', 'info#aoptrading.com');
$p->add_field('return', $this_script.'?action=success');
$p->add_field('cancel_return', $this_script.'?action=cancel');
$p->add_field('notify_url', $this_script.'?action=ipn');
$p->add_field('item_name', $CatDescription);
$p->add_field('amount', $payment);
$p->add_field('key', $key);
$p->add_field('item_number', $id);
$p->submit_paypal_post(); // submit the fields to paypal
//$p->dump_fields(); // for debugging, output a table of all the fields
break;
case 'success': // Order was successful...
echo "<br/><p><b>Payment Successful.</b><br /></p>";
foreach ($_POST as $key => $value) { echo "$key: $value<br>"; }
break;
case 'cancel': // Order was canceled...
echo "<br/><p><b>The order was canceled!</b></p><br />";
foreach ($_POST as $key => $value) { echo "$key: $value<br>"; }
break;
case 'ipn': // Paypal is calling page for IPN validation...
if ($p->validate_ipn()) {
// For this example, we'll just email ourselves ALL the data.
$dated = date("D, d M Y H:i:s", time());
$subject = 'Instant Payment Notification - Recieved Payment';
$to = 'info#aoptrading.com'; // your email
$body = "An instant payment notification was successfully recieved\n";
$body .= "from ".$p->ipn_data['payer_email']." on ".date('m/d/Y');
$body .= " at ".date('g:i A')."\n\nDetails:\n";
$headers = "";
$headers .= "From: Test Paypal \r\n";
$headers .= "Date: $dated \r\n";
$PaymentStatus = $p->ipn_data['payment_status'];
$Email = $p->ipn_data['payer_email'];
$id = $p->ipn_data['item_number'];
if($PaymentStatus == 'Completed' or $PaymentStatus == 'Pending'){
$PaymentStatus = '2';
}else{
$PaymentStatus = '1';
}
foreach ($p->ipn_data as $key => $value) { $body .= "\n$key: $value"; }
fopen("http://www.virtualphoneline.com/admins/TestHMS.php?to=".urlencode($to)."&subject=".urlencode($subject)."&message=".urlencode($body)."&headers=".urlencode($headers)."","r");
}
break;
}
?>
An extra class file: (can be found here) http://pastebin.com/auCdYhaR
The code is working fine, but I am having big issue now, I am trying to validate whether the payment is successful or not from the following lines and doing the action (adding 10 credits to the database for the user on session).
case 'success': // Order was successful...
echo "<br/><p><b>Payment Successful.</b><br /></p>";
foreach ($_POST as $key => $value)
{
/*echo "$key: $value<br>";*/
// Do the required action, **add 10 credits in the database for the user on session**
}
break;
Finally, the issue is when I click on the button from button.html page it redirects to the Paypal.php page and when I enter my PayPal login details, payment is successful
THERE COMES A SMALL LITTLE TEXT -> RETURN TO THE SENDER'S WEBSITE I NEED TO CLICK ON IT, WHEN I CLICK ON IT, IT WILL BRING ME BACK TO PAYPAL.PHP PAGE AND THEN THE CASE 'SUCCESS' IS FIRED. IF I MAKE THE PAYMENT AND JUST CLOSE THE PAYPAL PAGE WITHOUT CLICKING ON RETURN TO THE SENDER'S WEBSITE AND DIDN'T WAIT TILL THE PAGE PAYPAL.PHP LOADS WEBSITE COULDN'T VERIFY THE PAYMENT AND COULDN'T ADD THE CREDITS.
HOW CAN I AUTOMATE THIS PROCESS AND ADD CREDITS UPON SUCCESSFUL PAYMENT NOT UPON SUCCESSFUL RETURN TO THE PAGE PAYPAL.PHP.
THANKS

Answer 1

It sounds to me like you're confusing PDT and IPN. PDT works by sending data to your return URL, but that is not the recommended way to handle post-payment processing tasks.
That's where IPN comes into play, which is a silent POST of data to your listener URL regardless of whether or not the user makes it back to your return URL. That way that code will always run no matter what (assuming you've got everything configured correctly.)
Sounds to me like you're sort of mixing the two and getting mixed results because of it.