Calculate distance between two locations by Latitude and Longitude

The following code returns the distance between to locations based on each point’s longitude and latitude.

Passed to function:

lat1, lon1 = Latitude and Longitude of point 1 (in decimal degrees)

lat2, lon2 = Latitude and Longitude of point 2 (in decimal degrees)

unit = the unit you desire for results where: ‘M’ is statute miles (default)

‘K’ is kilometers

‘N’ is nautical miles

PHP

function distance($lat1, $lon1, $lat2, $lon2, $unit) {
  $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";

###Javascript

function distance(lat1, lon1, lat2, lon2, unit) {
	var radlat1 = Math.PI * lat1/180
	var radlat2 = Math.PI * lat2/180
	var radlon1 = Math.PI * lon1/180
	var radlon2 = Math.PI * lon2/180
	var theta = lon1-lon2
	var radtheta = Math.PI * theta/180
	var dist = Math.sin(radlat1) * Math.sin(radlat2) + Math.cos(radlat1) * Math.cos(radlat2) * Math.cos(radtheta);
	dist = Math.acos(dist)
	dist = dist * 180/Math.PI
	dist = dist * 60 * 1.1515
	if (unit=="K") { dist = dist * 1.609344 }
	if (unit=="N") { dist = dist * 0.8684 }
	return dist
}

Reference : http://www.movable-type.co.uk/scripts/latlong.html