[Sheryld]

вот выдержки из MAN:

Caution:
If you want your script to work regardless of register_globals, you need to instead use the $_SESSION array as $_SESSION entries are automatically registered. If your script uses session_register(), it will not work in environments where the PHP directive register_globals is disabled.

register_globals: important note:
Since PHP 4.2.0, the default value for the PHP directive register_globals is off. The PHP community encourages all to not rely on this directive but instead use other means, such as the superglobals.

Caution:
This registers a global variable. If you want to register a session variable from within a function, you need to make sure to make it global using the global keyword or the $GLOBALS[] array, or use the special session arrays as noted below.

Caution:
If you are using $_SESSION (or $HTTP_SESSION_VARS), do not use session_register(), session_is_registered(), and session_unregister().