What are the potential security risks of passing session IDs in URLs in PHP applications?

Passing session IDs in URLs in PHP applications can lead to security risks such as session hijacking and session fixation attacks. To mitigate these risks, it is recommended to use cookies to store session IDs instead of passing them in URLs.

// Set session ID in a cookie
session_start();
$_SESSION['user_id'] = 123; // Example user ID