For my store, I'm creating an optional file upload form for artwork after a customer has made a purchase. Thus far, I have edited the define_checkout_success.php with an upload form (I am using the CSRF token with the upload form). I have created an attribute for file upload for a product to do research and learned that the "number_of_uploads" get paramater is set to 1 for this specific product when submitting the form.

I can't seem to find where the process happens after that point. The file is uploaded, I can see it on my server and the database gets updated. I would like to use the same function that handles the process here (after adding a product to the cart) that's obviously already built into Zencart for my optional artwork upload.

So, I'm pretty sure I could just set the action of the form to a specific pages that already handles file uploads, but I can't seem to get everything in line.

Thanks for any information.