What potential issues could arise from using session variables to store user data in PHP?

One potential issue with using session variables to store user data in PHP is that they can be vulnerable to session hijacking or session fixation attacks if not properly secured. To mitigate this risk, it is recommended to use session_regenerate_id() function to generate a new session identifier on each request, making it harder for attackers to hijack a session.

// Start the session
session_start();

// Regenerate the session ID to prevent session fixation
session_regenerate_id(true);