Are there any potential security risks involved in transferring sessions between domains in PHP?

When transferring sessions between domains in PHP, there is a potential security risk known as session fixation. This occurs when an attacker sets a session ID before the user logs in, allowing them to hijack the session. To prevent this, you can regenerate the session ID after the user logs in, ensuring that a new session ID is generated and the old one becomes invalid.

// Start the session
session_start();

// Log the user in
// Your login logic here

// Regenerate the session ID
session_regenerate_id(true);