sessions and mysql: easy question

i'm using session on my page basically my need is this: certain values wil be set for every visitor some for only certain visitors (for example: only if they fill out their name&adress) when the session is closed i want the ones that have those values filled out (let's say their name&address) stored in a mysql-table i have 2 ideas: * only storing the ones needed in a mysql-table >> because of a lot of traffic and variables and places where they can modify them, i'd prefer to store all of it at closing the session: is this possible?? (since i don't have control on when they close the session: is it possible to have php run a mysql-query after their browser is closed, with their inserted data?) * storing all the sessions in a mysql-table, deleting the ones that aren't relevant >> pretty much the same question: how can I check on their variables after they've closed the session, and delete their record if needed? does this make sense? any other suggestions? anything most welcome grace michiel