What are common errors that may occur when trying to protect multiple pages in PHP using session management?

One common error when trying to protect multiple pages in PHP using session management is not properly checking if the user is authenticated on each protected page. To solve this, you should check if the user is authenticated on every page that requires protection by verifying the session variable that indicates the user is logged in. 

<?php
session_start();

if(!isset($_SESSION['logged_in']) || $_SESSION['logged_in'] !== true){
    header("Location: login.php");
    exit();
}
?>

Keywords

PHP session management authentication authorization error handling

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