Distance between lat/long coordinates

lat-long-distance

<script>
// from http://html5doctor.com/finding-your-position-with-geolocation/
	if (navigator.geolocation) {
	  var timeoutVal = 10 * 1000 * 1000;
	  navigator.geolocation.getCurrentPosition(
	    displayPosition, 
	    displayError,
	    { enableHighAccuracy: true, timeout: timeoutVal, maximumAge: 0 }
	  );
	}
	else {
	  console.log("Geolocation is not supported by this browser");
	}

	function displayPosition(position) {
	  console.log("Latitude: " + position.coords.latitude + ", Longitude: " + position.coords.longitude);
	  
	  // save lat long as cookies
	  // via http://www.satya-weblog.com/2007/05/php-and-javascript-cookie.html
	  document.cookie = 'lat='+position.coords.latitude;
	  document.cookie = 'long='+ position.coords.longitude;
	}

	function displayError(error) {
	  var errors = { 
	    1: 'Permission denied',
	    2: 'Position unavailable',
	    3: 'Request timeout'
	  };
	  console.log("Error: " + errors[error.code]);
	}
</script>

<?php 

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

  // grab from $_COOKIE

  $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;
      }
}

$lat = $_COOKIE['lat'];
$long = $_COOKIE['long'];

// echo user distance to set location (second set of lat long)
echo distance($lat, $long, 29.46786, -98.53506, "M") . " Miles<br />";
echo distance($lat, $long, 29.46786, -98.53506, "K") . " Kilometers<br />";
echo distance($lat, $long, 29.46786, -98.53506, "N") . " Nautical Miles<br />";

?>

via http://www.geodatasource.com/developers/php