ログアウト処理

<?php
 require_once('config.php');
 require_once('functions.php');

 session_start();


 $pdo = connectDb();
 if (isset($_COOKIE['○○○'])) {
 $auto_login_key = $_COOKIE['○○○'];

 setcookie('○○○', '', time()-86400, '/xxxx/xxxx/xxxx/');

 $sql = "delete from auto_login where c_key = :c_key";
 $stmt = $pdo->prepare($sql);
 $stmt->execute(array(":c_key" => $auto_login_key));
 }

 $_SESSION = array();

 if (isset($_COOKIE[session_name()])) {
 setcookie(session_name(), '', time()-86400, '/xxxx/xxxx/xxxx/');
 }

 session_destroy();
 unset($pdo);
 header('Location:'.SITE_URL.'login.php');
 ?>