Code Snippet

Calculate Distance Between Two Coordinates

  • Check if coordinates are the same
  • Calculate the difference in longitude
  • Apply the Haversine formula
  • Convert distance to miles
  • Convert miles to the requested unit (kilometers, nautical miles, or miles)
PHP 
function distance_between_two_points($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;
    }
  }
}