Simple php/paypal shopping cart - repost

I need a simple php/paypal shopping cart with the following specifications: I cannot provide the paypal information, as it is privileged. I'm fine with a straightforward "old fashioned" implementations, as is seen here ([login to view URL]), if necessary. I need a "pass-through" variable for each of the products (there are 5), and I need to be able to read that pass-through variable on the other end into a php variable in a script. This is really the reason I'm unable to build this myself. If someone orders item #1, #3, and #4, I need the paypal "success" page to provide me with php variables that says 1, 3, and 4, in other words.