How can I convert Hijri date to gregorian in PHP?

I would like convert this date:09/13/1436 (it is Hijiri) to 2015-06-30(it is Gregorian). I tried that:

function HijriToJD($m, $d, $y){
   return (int)((11 * $y + 3) / 30) + 354 * $y + 
     30 * $m - (int)(($m - 1) / 2) + $d + 1948440 - 385;
}


$date = HijriToJD(9, 13, 1436);

echo jdtogregorian($date);