Aaron Parecki

<?php
/* Calculates the distance in meters between two coordinates */
 
function gc_distance($lat1, $lng1, $lat2, $lng2) {
  return ( 6378100 * acos( cos( deg2rad($lat1) ) * cos( deg2rad($lat2) ) * cos( deg2rad($lng2) - deg2rad($lng1) ) + sin( deg2rad($lat1) ) * sin( deg2rad($lat2) ) ) );
}