当打开2个点击时，PHP删除cookie不能在safari上工作

Question

I delete cookie by command

unset($_COOKIE['login']);
setcookie('login', null, -1, '/');

It works well when I open 1 tap on safari. But if i open 2 taps it not working. The cookie not empty. When unserialize($_COOKIE['login']) i get the error:

Notice: unserialize(): Error at offset 0 of 7 bytes

It's ok on Chrome and Firefox.