会话取消设置每个变量？

Question

I only want to unset play_mode however the second line also unsets landing_site.

Why is this happening?

session_start();

session_unset($_SESSION['play_mode']);

echo $_SESSION['landing_site'];

Answer 1

Because, as per the documentation,

The session_unset() function frees all session variables currently registered.

Also, session_unset() takes no arguments.

If you only want to unset $_SESSION['play_mode'], then just do unset($_SESSION['play_mode']).