Since updating php to 4.2.0 from 4.1.2 it seems that the SID constant is no longer set when the session ID is not propogated via cookie.  I have session cookies completely disabled and have php compiled with --transparent-sid enabled.  The transparent sid seems to work fine, as the PHPSESSID=blah is properly added to all uri etc within the pages.  However in the specific case of using a Location: header through the header() function it is necessary to manually append the session id, In the past I had always done this through the use of the SID constant.  The SID constant however is apparently no longer being set resulting in my session not being set correctly.