logout.php

<?php
session_start();

//unset all the session variables
session_unset();

//destroy session
session_destroy();

//delete the session cookie
$params = session_get_cookie_params();
setcookie(session_name(), '', 0, $params['path'], $params['domain'], $params['secure'], isset($params['httponly']));

//redirect to login page
header("Location: login_page.html");
?>