distance-calculate-using-lat-long

 function distance($lat1, $lon1, $lat2, $lon2, $unit) {
    if (($lat1 == $lat2) && ($lon1 == $lon2)) {
      return 0;
    }
    else {
      $theta = $lon1 - $lon2;
      $dist = sin(deg2rad($lat1)) * sin(deg2rad($lat2)) +  cos(deg2rad($lat1)) * cos(deg2rad($lat2)) * cos(deg2rad($theta));
      $dist = acos($dist);
      $dist = rad2deg($dist);
      $miles = $dist * 60 * 1.1515;
      $unit = strtoupper($unit);
      if ($unit == "K") {
        return ($miles * 1.609344);
      } else if ($unit == "N") {
        return ($miles * 0.8684);
      } else {
        return $miles;
      }
    }
  }

echo distance(32.9697, -96.80322, 29.46786, -98.53506, "M") . " Miles"

echo distance(32.9697, -96.80322, 29.46786, -98.53506, "K") . " Kilometers"

echo distance(32.9697, -96.80322, 29.46786, -98.53506, "N") . " Nautical Miles"