What are the potential security risks associated with using a session-based login system in PHP?

One potential security risk associated with using a session-based login system in PHP is session fixation attacks, where an attacker can force a user's session ID to a known value and then hijack the session. To prevent this, you can regenerate the session ID after a successful login to ensure that the session ID changes and is not predictable.

// Start the session
session_start();

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

// Your login code here
// Verify user credentials and set session variables