What's next with PayPal IPN?

PHP
1

Hi all, I’m working in the payment process and thinking I will go with PayPal. I have taken a look at the following code from PayPal’s developer centre. Not sure how to implement it.

Do I have a submit button which when pressed runs the code on their site or is there something I’m missing? I’ve as yet never needed a payment gateway but that time has now come in my developing career and hoping someone can help me along that journey…

// PHP 4.1

// read the post from PayPal system and add 'cmd'
$req = 'cmd=_notify-validate';

foreach ($_POST as $key => $value) {
$value = urlencode(stripslashes($value));
$req .= "&$key=$value";
}

// post back to PayPal system to validate
$header .= "POST /cgi-bin/webscr HTTP/1.0\\r\
";
$header .= "Content-Type: application/x-www-form-urlencoded\\r\
";
$header .= "Content-Length: " . strlen($req) . "\\r\
\\r\
";
$fp = fsockopen ('ssl://www.paypal.com', 443, $errno, $errstr, 30);

// 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'];

if (!$fp) {
// HTTP ERROR
} else {
fputs ($fp, $header . $req);
while (!feof($fp)) {
$res = fgets ($fp, 1024);
if (strcmp ($res, "VERIFIED") == 0) {
// check the payment_status is Completed
// check that txn_id has not been previously processed
// check that receiver_email is your Primary PayPal email
// check that payment_amount/payment_currency are correct
// process payment
}
else if (strcmp ($res, "INVALID") == 0) {
// log for manual investigation
}
}
fclose ($fp);
}
?>
2

No, it’s not code you run when a button is pressed. It’s code you run when PayPal tells your website a payment has been made.
There’s a nice explanation of how it works over here: Paypal IPN tutorial | photoshop and PHP tutorials

3

Hey man, thank you so much for a reply. Looks very interesting reading, I will take a mooch through it. I’ve managed to do some pretty complex coding so I shouldn’t think it will be impossible, just in unknown territory.

I’ll post back on here if I hit any brick walls if that’s cool?

4

Sure thing :slight_smile:

5

One thing that a lot of people overlook with Paypal IPN scripts is that it gets called every time the status of a payment changes.

When someone pays by echeck the payment is pending until cleared by the bank (usually 3-4 days) and so the IPN script will generally get run to indicate that the payment is complete about four days after the person who made the payment has left your site.

6

Hey guys, I’m a little stuck on which PayPal product I need…I just need a Make a Payment button on the checkout which then takes the user to PayPal and then returns them to the site. Had a look on PayPal and all seem to be using their shopping cart…I’m stuck :confused: