How can PHP developers restrict access to certain files only to registered users?

To restrict access to certain files only to registered users, PHP developers can implement a user authentication system where users need to log in before accessing those files. This can be done by checking if the user is logged in before allowing access to the restricted files. 

<?php
session_start();

// Check if user is logged in
if(!isset($_SESSION['user_id'])) {
    // Redirect to login page if not logged in
    header("Location: login.php");
    exit();
}

// Restricted file content goes here
echo "Welcome, registered user!";
?>

Keywords

authentication authorization PHP sessions file permissions user roles

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