gistfile1.php

<?php
// Haversine
function distancekm($lat1,$lon1,$lat2,$lon2)
{
  $R = 6371; // km
	$dLat = deg2rad($lat2-$lat1); // to radians
	$dLon = deg2rad($lon2-$lon1); 
	$a = sin($dLat/2) * sin($dLat/2) +
	        cos(deg2rad($lat1)) * cos(deg2rad($lat2)) * 
	        sin($dLon/2) * sin($dLon/2); 
	$c = 2 * atan2(sqrt($a), sqrt(1-$a)); 
	$d = $R * $c;
	
	return $d;
}
?>