loosing session-id when using PostToHost

Hi, I want to post some data automatically from one php-script to another. Therefore, I use the "PostToHost"-function written by Rasmus Lerdorf (http://www.php-faq.com/postToHost.html) and it's work's very well. But unfortunately the current session-id get's lost and the script, that receives the post-data creates a new session-id. I've tried to send the current session-id as a post- and a get-parameter, but this didn't work either. Does anybody have an idea, how I can use the PostToHost-function without loosing the current session? thx, myri