PHP user login status operation class written based on session and cookie

final class UserLogin {
    public function __construct() {
    }
    public static function getUserInfo() {
        if (isset($_COOKIE["user_id"])&&$_COOKIE["user_id"]&&(trim($_COOKIE["user_id"])!="")) {
            if (isset($_SESSION["USER_INFO"]))
                return $_SESSION["USER_INFO"];
            $dao = new UserDao();
            $user = $dao->find($_COOKIE["user_id"]);
            if ($user) {
                $_SESSION["USER_INFO"] = $user;
                setcookie("docloud_sid", session_id(), time() + 36000);
                setcookie("user_id", $_COOKIE["user_id"], time() + 36000);

                if (array_key_exists("selected_prj_id", $_COOKIE))
                    setcookie("selected_prj_id", $_COOKIE["selected_prj_id"], time() + 36000);

                if (array_key_exists("selected_class_id", $_COOKIE))
                    setcookie("selected_class_id", $_COOKIE["selected_class_id"], time() + 36000);

                if (array_key_exists("selected_image_id", $_COOKIE))
                    setcookie("selected_image_id", $_COOKIE["selected_image_id"], time() + 36000);

                if (array_key_exists("test_image_ids", $_COOKIE))
                    setcookie("test_image_ids", $_COOKIE["test_image_ids"], time() + 36000);

                if (array_key_exists("upload_image_ids", $_COOKIE))
                    setcookie("upload_image_ids", $_COOKIE["upload_image_ids"], time() + 36000);
                return $user;
            }
        }
        self::clearCookie();
        return null;
    }
    public static function setUserInfo($userInfo) {
        $_SESSION["USER_INFO"] = $userInfo;
        setcookie("docloud_sid", session_id(), time() + 36000);
        setcookie("user_id", $userInfo->getId(), time() + 36000);
    }
    public static function isLogin() {
        if (self::getUserInfo()) {
            return true;
        }
        return false;
    }
    public static function delUserInfo() {
        self::clearCookie();
        session_destroy();
    }

    private static function clearCookie() {
        setcookie("docloud_sid", "", time() - 36000);
        setcookie("user_id", "", time() - 36000);
        setcookie("selected_prj_id", "", time() - 36000);
        setcookie("selected_class_id", "", time() - 36000);
        setcookie("selected_image_id", "", time() - 36000);
        setcookie("test_image_ids", "", time() - 36000);
        setcookie("upload_image_ids", "", time() - 36000);
    }
}
?>

2、在用户输入用户名、密码处调用来做相关判定

require_once 'Init.php';
// if logged in, logout
if (UserLogin::isLogin() && $_COOKIE["user_id"]==1) {
    UserLogin::delUserInfo();
}
else if (UserLogin::isLogin()){
    Utils::redirect('welcome');
}
$username = null;
$password = null;
$msg = "";
if (isset($_POST['username']) && isset($_POST['password'])) {
    $username = addslashes(trim(stripslashes($_POST ['username'])));
    $password = addslashes(trim(stripslashes($_POST ['password'])));
    // validate
    $errors = LoginValidator::validate($username, $password);

    if (empty($errors)) {
        // save
        $dao = new UserDao();
        $user = $dao->findByName($username);
        $last_login_ip = Utils::getIpAddress();
        $user->setLastLoginIp($last_login_ip);
        $now = new DateTime();
        $user->setLastLoginTime($now);
        $dao->save($user);
        UserLogin::setUserInfo($user);
        Flash::addFlash('登录成功！');
        Utils::redirect('welcome');
    }

    foreach ($errors as $e) {
        $msg .= $e->getMessage()."";
    }
}
?>