fread and session vars

Hi all, I'm using the fread function to read one of my php scripts and then produce a static page, within this script I'm using session variables. If I browse to the script normally then all appears to work correctly, however when I use the fread function the session variables are not being translated. I've tried adding & SID to the end of the URL but to no avail. Can anyone suggest a course of action. I'm reluctant to produce GET variables as there are many variables and this script will need to be used by multiple domains. Thanks, Zac