How to make a payment through Robokassa on the landing page?

Question

PHP

Good afternoon. There is a landing page in php, it sells processed photos. The bottom line is this, the user uploads a photo, processes it with filters, and then after payment, this photo is available to him in full size. I can't figure out how to provide the user with exactly the photo that he uploaded after payment. Please tell me how to connect.
There are no registrations on the site and the like...

Answer 1

Create an order with a unique number.
Order fields: photo id, price, user's soap.
Send it to the Republic of Kazakhstan to pay.
When the RK informs you that the payment has occurred (this may be later after the user has already completed all his actions and was returned to your site) - send him a link to download the finished photo via soap. All.
Well, if you like, remember this user with cookies and show him the same link on the site when he comes back there.
But building an interaction scheme on the assumption that he paid, returned to the site - and here is a photo for him, would be a big mistake. It is possible that the site will not yet know by the time he returns whether he paid for anything or not.

Answer 2

In case of successful payment, ROBOKASSA makes a request to the ResultURL, respectively, at this address there should be a delivery of goods (photos)

Answer 3

Payment without registration? Seriously? What will you do if the payment does not go through immediately? Force user not to close window for 3 days?
What about connection failure?
At a minimum, the user should have a unique link where he can pick up the order, but then the security issue arises. Anyone can take. So registration is required.
At a minimum, you need to take an email to which to send the result or a link to it.
But it's still not clear why not register.

Answer 4

Agree with previous speakers. You have to be connected to something. If you do not want registration, then either soap or generate a link and notify the visitor in capital letters that he needs to save the link somehow.