Distance as the bird flies

gistfile1.aw

<?php

function distance($lat1, $lon1, $lat2, $lon2) { 
	$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);  // distance in nautical miles
	//$miles = $dist * 60 * 1.1515;
	$km = $dist * 60 * 1.852; 
	return $km; 
}