How can PHP sessions be effectively utilized to manage user authentication and authorization in a web application?

To manage user authentication and authorization in a web application using PHP sessions, you can store user credentials in the session when a user logs in and check these credentials on each page load to determine if the user is authenticated and authorized to access certain resources. This can be achieved by setting session variables upon successful login and checking these variables on protected pages to ensure only authenticated users have access.

// Start the session
session_start();

// Check if user is logged in
if(isset($_SESSION['user_id'])) {
    // User is authenticated, perform authorization check if needed
} else {
    // Redirect user to login page
    header("Location: login.php");
    exit();
}