Authentication check via COOKIE?

Question

PHP

Hello. There is a registration/authorization form for the Database, and since I am a beginner programmer, I do not yet fully know how to work with Cookies, I wrote the forms. They create cookies in the browser for this website. But, how to check these cookies so that without authorization, the user could not climb other tabs?
Examples:
Authorization - ../admin/index.php/
The file that needs to be checked for cookies - ../admin/page/add.php
It needs to be done so that when an unauthorized user goes to ../admin/page/add.php threw on the form of authorization, and passed the authorized person. Help me please

Answer 1

Hint:
https://www.php.net/manual/ru/function.setcookie.php
https://www.php.net/manual/ru/function.empty.php
https://www.php.net/ manual/en/function.header.php -> you need to send
the Location header

Answer 2

It is necessary to use not cookies, but sessions . Cookies are sent from the browser, so they can be easily forged by a hacker who will get full access to the admin panel in a couple of minutes, and session variables are stored on the server where the hacker does not have access.