PHP Sessions versus POST resubmission -

i'm polishing , getting first application ready production when started doing research on optimizations. in our application (as tested) average user sends 7 requests server per minute.

the application set use randomly generated key validation. if @ time user's validation key not match key in database, key changed again , user logged out of application. due nature of application, going "back" on app won't change or break validation key, that's never issue. way validation key incorrect else logging account, trying jack login session.

there's lot of posts on interenet, of them shaming use of $_session variables, , of them praising them. of them saying there's no harm in usage, , saying adds quite bit of response time requests. data needs stored in $_session in case integer , uuid.

i'm trying figure out if sending these variables server client (and sending updated uuid client) every request more efficient loading , storing uuid php session every request.

as had said before, there's enumerous amount of posts on internet have conflicting information , of them years ago, , considering technology changes time, figured worth asking here in 2015.