What are some potential security risks associated with using the `$_SESSION` variable in PHP?

One potential security risk associated with using the `$_SESSION` variable in PHP is the possibility of session hijacking or session fixation attacks. To mitigate this risk, it's important to regenerate the session ID whenever a user's privilege level changes or upon successful login. This helps prevent an attacker from using a stolen session ID to gain unauthorized access to a user's account.

// Regenerate session ID upon successful login
session_start();
session_regenerate_id(true);