[PHP4] getdate() and the Time zone?

I have a problem where if I change the time zone PHP doesn't recognize it in getdate(). For example, if the time is 12:05 in Europe/London and I change the time zone to US/Mountain, the hour index in the array from getddate() returns a 19 instead of a 12. I've tried setting the TZ environment variable before the getdate() call and it doesn't make a difference. I can fix the problem if I do a "cold" restart of Apache (sending a HUP or USR1 signal won't cut it), but I'd rather not since it can cause the PHP session to break, giving the user an empty page. Any ideas to solve this problem besides a system() call to get the actual time? Thanks, Chris