Safari ignore "expire" cookie directive

Safari on MAC, iPhone and iPad is ignoring expire directive of cookie creation and it clear cookies after closing the browser, can you please explain why, and how can i resolve this issue.

This is the php code that i use to create cookie.

setcookie('cookie_test', 'cookie_data', time() + 60 * 60 * 24 * 720, "/", "");

Thank you