(PHP 4, PHP 5)
session_unregister — Unregister a global variable from the current session
session_unregister() unregisters the global variable named name from the current session.
自 PHP 5.3.0 起，已经废弃此函数。强烈建议不要应用此函数 。
The variable name.
成功时返回 TRUE， 或者在失败时返回 FALSE.
Note:
If $_SESSION (or $HTTP_SESSION_VARS for PHP 4.0.6 or less) is used, use unset() to unregister a session variable. Do not unset() $_SESSION itself as this will disable the special function of the $_SESSION superglobal.
This function does not unset the corresponding global variable for name, it only prevents the variable from being saved as part of the session. You must call unset() to remove the corresponding global variable.
If you are using $_SESSION (or $HTTP_SESSION_VARS), do not use session_register(), session_is_registered() and session_unregister().