payment thru headquarter website on the same server

Hello, I have 2 zen cart websites on the same server, and one of them is the headquarter website. It might sound counterintuitive, but i would like to have the headquarter website handle the paypal payments when people are ordering from the other zen cart store. For example, someone order things from JewelryStore, chooses paypal payment, it redirects to the HeadQuarter website directory to process the payment (i don't mind people seeing text that says "payment for order on HeadQuarter" or such), then once the transaction is completed people are redirected to the Jewelry website that says the transaction is completed (or it wouldn't be too bad if it stays on the HQ website after transaction). Does anyone has hints at where/how to modify the payment module files ?

While this sounds interesting, it is neither practical, nor easy (if it is indeed possible at all).

Critical to the purchase and checkout>>>payment process, is the maintenance of session ID's and transaction completion, and the full circle has to be accomplished within that framework. For the order to "complete", and to register as "complete", the purchaser has to return to the originating site so that all the "loose ends" can be finalised and written to the database.

As you may know, different zencart sites can use a single PayPal account. The system is "clever" enough to know where to send people back to after they have made a purchase.

What would be easier (and a lot better) to do, is use your checkout_success page to invite visits to associated sites, by advertising some attractive offers from those site, on the checkout_success page.

We do this with one of our clients who has TWO branches to his business. The first branch is office furniture retail. The second is office interior design and planning.

People buy their furniture on the retail site, then when they get to checkout_success, they are invited to visit the other website to take advantage of interior design consultations, so that someone can help them arrange their new furniture and make the office look really nice.

Your issue appears to be more of a "logistical" issue, involving how you "manage" your business. It may be more sensibile to do this outside of the framework of your eComm site(s).

Maybe just putting the payment module files (slightly modified to know the good paths) in a directory on the headquarter website (ex: headquarter.com/somedirectory/) ? Would that preserve the session id ? Basically i just want the paypal page to be redirected from the HQ domain, it's not important if it is visible to the user or not. If it needs to, the HQ website can have access to the other website database because they are both on the same server account.

To be clear i mean putting the paypal payment module files for the Branch on headquarter.com/somedirectory/, independent of the headquarter's payment module files.

And after the paypal transaction is completed it is redirected back to the branch's website to finish the order process.

I don't understand WHY you want what you think you want.

Please explain the business problem that precipitated your post. What exactly is the problem you're trying to solve with all of this "headquarter site processing the payments" stuff.
Surely there's got to be some specific reason why you felt you needed to go down this particular road, asking the questions you're asking. You've jumped to a planned "solution" and now you're asking us how you can implement the solution *you* came up with .... but I submit that your "solution" isn't a solution. So, explain the reasoning and all the thinking and problems and issues that led up to it, and maybe we can help come up with a much better solution that works more effectively.

Are you:

1. Trying to COLLECT INFORMATION relating to the paypal transaction, or
2. Trying to DRIVE A PROCESS (ie: get a function to operate)?

If you are trying to collect information, then there is NO POINT moving the paypal php files.

You need rather to build a "bridge" between the HQ system (whatever that means), that collects the data AFTER all the essential procedures have been completed.

There is no logical reason why you would want to move the processing functions.

It is like trying to wire up a flashlight with the batteries on the outside, when the flashlight works perfectly with the batteries where they are designed to go... inside.