We sell subscriptions through zen cart - subscribers are managed through a custom mysql db and php admin system. when the order is completed, if a sub is one of the items, info is inserted into the db, etc. We use the paypal module.

the way i have it working now, however, it runs through the tp_checkout_success_default.php page because I wasn't able to figure out the right place to insert my code. Obviously this is not a good way to do it for a few reasons.

My question - what file am i looking for? I need to find the code that verifies that payment has been completed so I can check the order contents and plug in the subscription code.

Thanks!