Google Analytics, out-of-browser target?

Question

Google Analytics

Hey gays!
Does anyone know how to complete a compound goal in GA outside of the browser? those. there is the first part of the goal starting from the main page, and it ends after the purchase of the product. And buyers do not always return from the payment service back to the store to the "thank you for your purchase" page. Therefore, we need the option of registering the completion of the goal by the API chtoli, or something else, by a php script in general.
Thank you.

Answer 1

measurement protocol

Answer 2

There is no such possibility that, for example, you want to find out outside the store?

Answer 3

I want to note in the GA that the order was paid. And this is known only to my listener of data from the payment system (just a php receiver).