Questions about the range of sessions

Concerning the range of sessions, the session_start () and session_register () functions are used during user login. they are defined before the tag & lt; http & gt, the session_unregister () function is used to log out. it runs in & lt; body & gt. & Nbsp; questions about the range of sessions
The session_start () and session_register () functions used during user login are marked As defined earlier in, LOGOUT is the session_unregister () function, which is.



I wantTo determine whether a user is a legal user. If (isset ($ AB )&&! Empty ($ AB) is used to display a specific object, but the current situation is:

1. After I log out, if I click index. php on the address bar? AB = user and then enter the user's interface (the div part appears)

2. I did not log out, but when I go to another page and return again through that page, the user page disappears again. why?

Thank you.



Note: in a function, I use global $ AB when writing a function. Otherwise, I cannot log on to the function for the first time.

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Did not understand. Answered by yourself?
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I suspect that not the same person's operations ......
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User logout. Yes.
Unset ($ _ SESSION );
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For example, after you log on successfully,
$ _ SESSION ['admin'] = '***';
Logout:
Unset ($ _ SESSION ['admin']);