I have spent over 2 hours scouring the net trying to figure this out. I am trying to stop multiple form submission any faster than 60 seconds. Here is what I am using.

session_start();
if (!isset($_SESSION['last_submit']))
    $_SESSION['last_submit'] = time();

if (time()-$_SESSION['last_submit'] < 60)
    die('Post limit exceeded. Please wait at least 60 seconds');
else
    $_SESION['last_submit'] = time();

I found this bit here on the site but haven't been able to figure anything else out as far as getting it to work. I have this bit of code on my page at the beginning that does the DB query with the previous pages POST results. Do I need to set $last_submit to a certain value? Any help is appreciated.