//example
// $dformat = "-"
// $endDate = 2008-01-15
// $beginDate = 2008-01-02
//
// returns 13

function dateDiff($dformat, $endDate, $beginDate)
        {
                $date_parts1=explode($dformat, $beginDate);
                $date_parts2=explode($dformat, $endDate);
                $start_date=gregoriantojd($date_parts1[0], $date_parts1[1], $date_parts1[2]);
                $end_date=gregoriantojd($date_parts2[0], $date_parts2[1], $date_parts2[2]);
                return $end_date - $start_date;
        }