session_start(); // Perform login action if ($_POST['username'] == 'admin' && $_POST['password'] == 'password') { $_SESSION['loggedin'] = true; } // Check if user is logged in if (!isset($_SESSION['loggedin']) || $_SESSION['loggedin'] !== true) { // Redirect to login page header('Location: login.php'); exit; } // Perform authorized action if ($_SESSION['role'] == 'admin') { // Do admin-specific action } else { // Do regular user action }This code uses PHP's built-in session management to track the user's authentication status and authorization level. The session data is stored on the server and can be accessed from any page on the same domain. The package library used in this example is the built-in `session` extension of PHP. Other package libraries that might be useful for a User app include: - Authentication libraries such as `php-jwt` for handling JSON Web Tokens or `password-hash` for securely hashing passwords. - Authorization libraries such as `rbac` for implementing role-based access control. - User management libraries such as `userfrosting` or `laravel-passport` for managing user accounts and authentication in a web framework context.