On NETTUTS.com a recent tutorial has been posted about the integration of your PHP application with PayPal's Instant Payment Notification system.

Today we are going to combine Paypal with PHP to allow for the easy processing of payments on your website.

You'll need a Premier PayPal Account to get it all working as well as already have a server with a working PHP installation (there's no setup and install for that in this tutorial). There's ten different steps in the process and screenshots and code are provided the whole way:

• Creating a PayPal Account
• Enable IPN
• Building a Simple HTML Page
• Building a PayPal Button
• Writing ipn.php
• Creating the Database
• Account Creation
• Emailing the Login Credentials
• Invalid Payment Email
• User Login