You can append the seesion ID to any urls or form actions with
<?=SID; ?>
<A HREF='someurl.com?<?=SID; ?>'>Click Here</A>
If cookies are enabled, this has no affect, as it is not neccessary to append it to a url if cookies are enabled. If cookies are enabled, SID has no value, so no harm is done. If they are disabled, SID holds the session ID and passes it to the next page. If trans_id was enabled when PHP was compiled, this all happens automatically, you do not need to append it yourself.
Keep in mind, session_start() has to be called on any script that uses sessions, or it will not look for the session variables.