paypal ipn - instant payment notification script
if you are working with Paypal as your payment processor you certainly have heard of Instant Payment Notification supported by Paypal to instantly verify an customer purchase. By IPN turned on for your account, every time an customer purchases an item Paypal will post all the specific transaction details plus an security key to an url which is set from your side at your Paypal account profile. by receiving this transaction details, you will have to pass back the string to Paypal in order to prevent fraudsters from posting to your processing script. Paypal will then perform an check of your passed back data and if ok sends an verification of that transaction. exactly this routine handles the pp_ipn script at your side and also stores the relevant data foreach purchase in a single flat text file. you may set various parameters to perform checks on the Paypal transaction details, like for example your receiver email address, payment amounts, payment currencys, item names. if all checks perform ok the transaction will be marked as unlocked, if not it will be recorded as locked. now you may use this stored data to immediately process your customers purchase as you have allready the verification of the purchase from Paypal. there is also a second script, which will cooperate with the IPN verification script. this script allows the opening of an member account at your website, which will be protected by .htaccess and .htpasswd. so for example if you are selling digital goods or some subscription service this might be the ideal complimentary script to immediately process your customers purchase. the script will ask your customer for the Paypal email address she/he used for the purchase, based on that address the purchase will be verified with the previously stored data from your IPN script, if ok, the script will record the email address and the password in your .htpasswd file, then the newly created account data is displayed to your customer along with an protected member area url so they may login instantly. this confirmation and the account details are also mailed to the customers email address.