I still don't get it

I've brought this up in reference to other questions but haven't got a straight answer. Suppose I've created a session variable: session_register("foo") and receive a posted form with the input field "bar". If register_globals = off, I can only access the form-field like this: $HTTP_POST_VARS["bar"] and the session-variable like this: $HTTP_SESSION_VARS["foo"] If I set register_globals = on, the form-field can be accessed in two ways: $bar and the previous $HTTP_POST_VARS["bar"] but the session-variable only with: $foo and a new array $GLOBALS["foo"] My question: What happened to $HTTP_SESSION_VARS? And why, since $HTTP_POST_VARS is still accessible? - Carsten