session_start(); if (!isset($_SESSION['isLoggedIn']) || !$_SESSION['isLoggedIn']) { header("Location: login.php"); exit; } // rest of secure page code goes hereIn this example, we first start a PHP session using the session_start() function. Then we check if the isLoggedIn variable is set in the session, and if it is not or if it is set to false, we redirect the user to the login page using the header() function. Finally, if the user is logged in, we can continue executing code for the secure page. As for the package library, the isLoggedIn function is built-in to PHP and does not require any external packages or libraries.