How reliable are sessions in php?

Question

PHP

Hello!
I have been working on php for a long time and always store important data of logged in users in sessions
. Including when a user logs in, I set $_SESSION['online']=true
And when performing important operations, I check that online is equal to true
And I thought, is it safe? Can't the user somehow easily influence the contents of the session?
Indeed, unlike cookies, session data resides on the server, right?
If the sessions are not secure, please suggest options for a secure solution

Answer 1

The application code and the developer's brain are responsible for the reliability of sessions.
PHP has long taken care of the security of sessions when working with them.