SQL session handling + Memcache?

Question

PHP

I set my session_set_save_handler, I save sessions in the database...
But how can I add memcache as well?
to put checks and cache them in the methods specified in session_set_save_handler (open, read, write, ...)
I think it's useless...
How does the session work?
I got the session data from the database, does it create a temporary file and use the data from there, does it save it to the database when the session is closed?
or all processing in the functions specified in session_set_save_handler (open, read, write, ...) ?
if yes, then work with Memcache can be put there, but I'm not sure how it all works...

Answer 1

to cache in the methods specified in session_set_save_handler (open, read, write, ...)
I think it's useless...

Why is it useless? The most obvious way is.