- You put a form (hidden or with bits visible) that POSTs data to Paypal
- This brings the user to Paypal where they can pay using either a credit card or their Paypal account
- As part of processing the user's payment, Paypal takes key information about the user's payment e.g. transaction id, amount, and other sundry details and POSTs them to a custom instant payment notification URL (as it happens to be called) on your site
- This URL is hopefully hosts a script or other form of code that can pick up all the POSTed IPN variables and POSTs back the information with one extra variable to validate the information
- Once this POST back to Paypal returns with a success status the application can record the user's payment and credit them appropriately.
Friday, January 16, 2009
Paypal IPN and mc_fee
I encountered an interesting problem today with accepting payments for an online registration solution I wrote for a non-profit organization. The application accepts payments using Paypal's Instant Payment Notification feature. IPN works as follows: