How can a PHP developer create a login area that allows users to stay logged in across different pages?

To create a login area that allows users to stay logged in across different pages, PHP developers can use sessions to store user login information. By setting session variables upon successful login and checking these variables on each page, users can remain authenticated as they navigate through the website.

// Start the session
session_start();

// Check if user is logged in
if(isset($_SESSION['user_id'])) {
    // User is logged in, allow access to content
} else {
    // User is not logged in, redirect to login page
    header("Location: login.php");
    exit();
}

// Example of setting session variables upon successful login
$_SESSION['user_id'] = $user_id;
$_SESSION['username'] = $username;