You could try something like:

Code:
$date1 = date('Y-m-d', strtotime('2002-03-04'));
$date2 = date('Y-m-d', strtotime('2002-03-02'));

$a = strtotime($date1);
$b = strtotime($date2);

$diff = getdate(strtotime($date1) - strtotime($date2));

echo $diff['mday'];
Look up getdate() in the manual for more info.