Paypal IPN questions

[Red Squirrel]

I am implementing a new donation system on my game server, where when people donate, they will get points added to their game account.

Basically, they will double click a donation stone in the game, it will generate a random ID tied to their account, and open their browser to the donate page, with that ID embedded in it. They enter the amount they want to donate, and hit submit.

At this point I get an IPN notification, and it will set a flag in the database so that transaction ID is cleared, and the player will get their points.

The problem I am having is, how do I send the generated transaction ID to paypal and how do I make it get included in the IPN message? I can't seem to find anything about that in their documentation.

Or, am I overthinking this, is there a better way of doing this, perhaps some kind of 3rd party credit card handler that has a better API or something?

 

[Red Squirrel]

Through trial and error think I got it. It seems kinda dirty though, but it works... as long as I ensure that if tampering wont do anything, then I should be set.

Basically if someone does tamper with it, they're only going to screw up their order and not get anything out of it. I'll have to test this further of course, but now that I got this working, it's all minor details from here.

Basically I had to add a field named os1 in my button form, then I just put what I want in the value. In my case it's just generated by a $_GET which will be generated in game when the user clicks the stone. In the IPN message, that field actually comes back as option_selection2.