logout.php

<?php
session_start();

// Disable caching
header("Cache-Control: no-cache, no-store, must-revalidate"); // HTTP 1.1.
header("Pragma: no-cache"); // HTTP 1.0.
header("Expires: 0"); // Proxies.

// Unset all of the session variables
$_SESSION = array();

// If it's desired to kill the session, also delete the session cookie.
if (ini_get("session.use_cookies")) {
    $params = session_get_cookie_params();
    setcookie(session_name(), '', time() - 42000,
        $params["path"], $params["domain"],
        $params["secure"], $params["httponly"]
    );
}

// Destroy the session.
session_destroy();

// Remove cookies
setcookie('user_id', '', time() - 3600, '/');
setcookie('user_type', '', time() - 3600, '/');

// Redirect to login page
header("Location: login.php");
exit();
?>