session variables and page interrupt via a refresh

Hope someone can help on this one. Say you have a FORM processing page that does lots of stuff, so it takes many seconds to execute. Say the user gets impatient and hits the Refresh button while the processing page is only half completed. Here's the question: do any changes to session variables that happened during the first half of the page get saved to the session file? Does a page have to terminate normally (end of code, or call to exit() or die()) for the session save to work, or does it work even when the page terminates abnormally? Kirk