QIWI REST protocol. I don’t understand how to work with this thing at all?

Question

PHP

It is necessary to issue an invoice to users, then get the status of this invoice from Qiwi, and if it is paid, then certain actions are performed ...
If I understand correctly, the scheme is as follows:
- the user clicked "pay" on the site;
- then I form a request for invoicing;
- after that, I receive a response that the invoice has been issued and is awaiting payment;
- the user pays the bill;
- qiwi sends a notification about the status of the account;
- I send a response to the notification, supposedly everything is OK;
In words, everything seems to be clear, but the technical part is not particularly.
REQUEST EXAMPLE:
PUT /api/v2/prv/2042/bills/BILL-1
Accept: text/json
Authorization: Basic MjA0Mjp0ZXN0Cg==
Host: w.qiwi.com
Content-Type: application/x-www-form-urlencoded; charset=utf-8
user=tel%3A%2B79031234567%26amount=10.0%26ccy=RUB%26comment=test%26lifetime=
2012-11-25T09%3A00%3A00
What is it anyway? It is clear that this should be shove into the php file, but how to send this request?
How to form it? Suppose the site has a form in which the user enters his phone number, comment (optional), then this data is written to variables or to the database? And then a new php-file is formed from this data, in which the request itself is located?
And how to accept the answer from kiwi? Does the response seem to come in JSON or XML?
Documentation: https://static.qiwi.com/ru/doc/ishop/protocols/Onl...

Answer 1

how to send this request?

With CURL or another library