sessions handling

Hi folks, Have no idea is it the proper group to ask my question, any way here it is: We have two instances of apache/mod_php running on 80 and 443 ports accordingly. For both mod_php we have the same dir (/tmp) to store session information. Is it possible to mix sessions data up if user switches between 80 and 443 ports? I mean what if when user surfs over 80 port and has already sessionID in this mod_php context(PHPSESSID stores in cookie), then he jumps to 443 instance, would that mod_php correctly find proper session file? Is it possible that PHPSESSID in 443 context hasn't been initialized and mod_php won't get proper file? Regards, Dima Ruban