How to check where the request came from?

Question

PHP

Please tell me this moment:
I work with the interkassa and after the operation with the payment, the interkassa sends a request to the interaction url, How can I check if this interkassa really sent the data.
That is, how to check from where (from which ip or domain) did the post or get request come from?

Answer 1

support.interkassa.com
«
When sending a payment notification, the Interkassa Payment Interface service transmits the payment details and a control signature, which allows checking the invariance of the transmitted data. The merchant can perform a data integrity check using a verification signature.
»

Answer 2

God saves man, who save himself. I also thought to check where the request came from, you never know. Thank you all very much.

Answer 3

$_SERVER['HTTP_REFERER'], more details here: php.net/manual/en/reserved.variables.server.php