// Initialize session session_start(); // Check if user is logged in if(isset($_SESSION['user_id'])){ // Get user ID $user_id =$_SESSION['user_id']; // Query database for user information $user = Auth::get_user($user_id); //Display user information echo "Welcome " . $user['username'] . "!"; }In the above example, we first check if the user is logged in by verifying that their `user_id` is stored in the session. If the user is logged in, we then use the `Auth::get_user` function to retrieve their user information from the database. We then display the user's retrieved username. This code example suggests that `Auth` is a package or library that contains the `get_user` function for querying authentication information. It is likely that this package also includes other functions for user authentication and session management.