A simple shopping cart with check receipt number?

Question

PHP

Good evening everyone.
Interested in creating a simple shopping cart, for example, for selling digital goods, so that when choosing a product, a person is transferred to a page where there will be a field with a receipt number that a person receives, for example, when paying through QIWI, that is, a person enters a receipt number, this number is received the administrator, drives into the database that it is paid and a person can click, for example, the button next, receiving on the screen the inscription you order is paid. In other words, until the person provides the number of the paid receipt and the administrator adds it to the database, it will not be possible to press the button further and receive a response that the order has been paid.

Answer 1

receipt number that a person receives, for example, when paying through QIWI

https://corp.qiwi.com/business/onlineshops.action