mencari selisih tanggal dengan fungsi GregorianToJD()

 class hitungTelat{  
      function berhitung($checkout){  
           $today = date("Y-m-d");  
           $m = date("m", strtotime($today));  
           $d = date("d", strtotime($today));  
           $y = date("Y", strtotime($today));  
           $m2 = date('m', strtotime($checkout));  
           $d2 = date('d', strtotime($checkout));  
           $y2 = date('Y', strtotime($checkout));  
           $a=GregorianToJD($m, $d, $y); //today  
           $b=GregorianToJD($m2, $d2, $y2); //checkout date  
           $telat = $a - $b;  
           if($telat<=0)  
                $telat=0;  
           return $telat;  
      }  
 }  
 //$tel = new hitungTelat();  
 //echo $tel->berhitung("2012-07-23"); //kalau today=2012-07-25 maka hasilnya = 2