How can a PHP developer ensure that a user remains logged in even after leaving and returning to a website?

To ensure that a user remains logged in even after leaving and returning to a website, a PHP developer can use sessions to store user login information. By setting a session cookie with a long expiration time, the user can stay logged in across multiple visits. Additionally, the developer can check for the session cookie on subsequent visits to automatically log the user back in.

// Start the session
session_start();

// Set a session cookie with a long expiration time (e.g., 1 week)
$session_expiration = time() + (7 * 24 * 60 * 60); // 1 week
setcookie(session_name(), session_id(), $session_expiration, '/');

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