how can i update the value of a column in my table when the current tab close or navigate to another page?

I have a page and i named it to mypage.php.I have a table MyTable with a column STATUS.I want to update the status to T when the user enters to the page and change to F when the user leaves or close from the page. I tried with onbeforeunload with JS.Help me any way.thanks in advance. :)

via Chebli Mohamed