Why does authorization fail when caching is enabled by the host?

Question

PHP

I didn't know how to phrase the question correctly. The situation is as follows:
The hoster has enabled caching of my site. And after that, by clicking on any link, I log in under one user, then under another. My username is displayed on the top right. Sometimes there is a logout at all.
I store the user id in a cookie.
How does this happen?

Answer 1

Dynamic pages get into the cache, they must be excluded from there. The solution depends on what kind of cache is used on the hosting.
Look, maybe there is no cache by extension, for example: *.php