php variables.

Hi there, I am pretty much a newbie, I was wondering what php session variables are? I am creating a table with php that uses mySQL "create temporary table" based on user specified columns and some where clause stuff. The page then displays the contents of the table with the table headings as hrefs that allow the user to sort the table. Only problem is when the page reloads to show the new sorting the temporary table needs to be rebuilt. I know of to ways to pass the varibles I need, either through url params or saving them as a cookie, and then parsing them out again. Is there a better way or am I on the right track. Thanks. Steve.