Substituting local script data?

Question

PHP

Dear, tell me how to solve the following problem.
There is a php script encoded with an ioncube (cannot be decoded)
When it is launched, it sends a request to the server (site.ru/?key=88888)
In response, it receives a processed key of the form "55555"
It generates and passes validation, it is apparently by the salt of which I Don't know.
There is already a working request-response (88888-55555)
How to replace the sent request so that the script passes validation by key and starts?