PayPal Express Checkout (IPN used by other script) integration
The faster, safer way to send money, make an online payment, receive money or set up a merchant account.
PayPal Express Checkout integrates using IPN callback even if the callback is used by other system (e.g. shopping cart).
Note! This is description of integration with PayPal Express Checkout if you use PayPal buttons on your web pages. If you use PayPal as a processing system in your shopping cart, use the method for integrating with shopping cart,not these steps.
PayPal button
Now add the following code into EVERY PayPal button form:
<input type="hidden" name="custom" value="" id="pap_dx8vc2s5">
<script id="pap_x2s6df8d" src="https://URL_TO_PostAffiliatePro/scripts/notifysale.php" type="text/javascript">
</script>
This will ensure that referrer will be stored to the custom field.
Example
Example of updated PayPal form:
<!-- Begin PayPal Button -->
<form action="https://www.paypal.com/cgi-bin/webscr" method="post">
<input type="hidden" name="cmd" value="_xclick">
<input type="hidden" name="business" value="paypalemail@yoursite.com">
<input type="hidden" name="undefined_quantity" value="1">
<input type="hidden" name="item_number" value="Product Name">
<input type="hidden" name="amount" value="19.95">
<input type="hidden" name="image_url" value="https://yoursite.com/images/paypaltitle.gif">
<input type="hidden" name="no_shipping" value="1">
<input type="hidden" name="return" value="http://www.yoursite.com/paypalthanks.html">
<input type="hidden" name="cancel_return" value="http://www.yoursite.com">
<input type="hidden" name="custom" value="" id="pap_dx8vc2s5">
<script id="pap_x2s6df8d" src="https://URL_TO_PostAffiliatePro/scripts/notifysale.php" type="text/javascript"></script>
<input type="image" src="http://images.paypal.com/images/x-click-but5.gif" border="0" name="submit">
</form>
<!-- End PayPal Button -->
Integration 2
Now the IPN callback is pointed to your script. This callback has to be forwarded also to PAP paypal.php script, which url is https://URL_TO_PostAffiliatePro/plugins/PayPal/paypal.php.
In case, your paypal processing script is in PHP, you can use following code to accomplish that. You can place it at the beginning of your processing file.
/* PAP integration */
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "https://URL_TO_PostAffiliatePro/plugins/PayPal/paypal.php");
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $_POST);
curl_exec($ch);
/* end of PAP integration */
This will ensure that whole IPN callback will be forwarded without affecting your original script
This is all that is required. Now whenever there’s sale, PayPal Express Checkout will use its IPN function to call our sale tracking script, and system will generate commission for the affiliate.

Explore seamless integrations with Post Affiliate Pro to enhance your affiliate marketing strategies. Discover solutions for e-commerce, email marketing, payments, and more, with easy integrations for platforms like 1&1 E-Shop, 2Checkout, Abicart, and many others. Optimize your affiliate network with these powerful tools.
Effortlessly integrate your e-commerce site with Post Affiliate Pro and boost your affiliate program's success. Our expert team ensures seamless integration with your payment processor, handling technical issues along the way. Enjoy a free trial and free integration service, saving you time and maximizing your ROI. Join now and experience top-notch affiliate management with over 500 integration options.
The leader in Affiliate software
Post Affiliate Pro offers a comprehensive affiliate software platform to manage multiple affiliate programs with ease. Enjoy no setup fees, 24/7 customer support, and a free 1-month trial. Ideal for small and large businesses, it features precise tracking, automated workflows, and customizable tools to boost your affiliate marketing success. Try it now and streamline your affiliate operations effortlessly!