PHP / HTML - if user load page without passing a variable redirect user

Question

So if i have a profiles page such as localhost/profile.php?u=user How can i redirect the client to an error page if he doesn't specify the "u" such as localhost/profile.php without the ?u= variable?

Is it possible?

Answer 1

<?php
if(!isset($_GET['u']) || empty($_GET['u'])) header('Location: page-to-reidrect.php');