http://www.php.net/issethttp://techtalk.virendrachandak.com/php ... z2oobovYAy
This will do exactly as it says. If the variable $_POST['add'] is
set then TRUE will be returned (unless the value is NULL).
$_POST['add'] will only be set if you have post
ed a form containing an input with the name "add" or if you have set a value for it yourself in the code.