function hitung_umur($tanggal_lahir) {
        list($year,$month,$day) = explode("-",$tanggal_lahir);
        $year_diff  = date("Y") - $year;
        $month_diff = date("m") - $month;
        $day_diff   = date("d") - $day;
        if ($month_diff < 0) $year_diff--;
        elseif (($month_diff==0) && ($day_diff < 0)) $year_diff--;
        return $year_diff.' tahun '.$month_diff.' bulan '.$day_diff.' hari';
    }