/**
* example: date_diff("2007-04-29", "2007-05-01") -> 2
*/
function date_diff($start, $end)
{
        $s1 = split("-", $start);
        $s2 = split("-", $end);
        $x1 = gregoriantojd($s1[1], $s1[2], $s1[0]);
        $x2 = gregoriantojd($s2[1], $s2[2], $s2[0]);
 
        return $x2 - $x1;
}