How to implement authorization in another application through a PHP script?

Question

PHP

Hello! Such a question: suppose I have some kind of website (or web application) (for example, phpMyAdmin), and there is a script with a button, when clicked, the client should automatically log in to PMA (or another application). Where to dig, and how can authorization be made secure so that the password is not stolen in the process of transferring data from one script to another?
A ready-made solution is not needed (although, if there is one, it is also possible), tell me where to dig, an algorithm of actions.

Answer 1

1. Open the debugger (browser dev tools) in phpmyadmin, log in while watching how the request flies
2. Repeat the request, only from the script, using some http client, for example guzzle
3. As soon as it starts, screw all sorts of secure things