sessions and http request serialization

Hi all, I believe, and please correct me if I'm wrong, that php sessions force all http requests from a browser to be handled serially. That is, if I'm using a browser and php sessions, I can only make one request at a time of the web server. The first request must complete before the second request begins. I presume this was done so that two http requests cannot change session variables simultaneously and therefore lead potential name space problems. I have a need to run two php driven http requests simultaneously and also want to continue using session variables. Is there a way to tell php, that I am done using session variables for this http request and to allow the next hit to the web server to proceed without blocking? I see in the source that there exists a function called: void _php_session_shutdown(void *data); I think this is what I want, but it is not visible from within php itself. Ideas? Thanks --pk