Calculate the Distance Between Two Geo Coordinates

gistfile1.php

<?php
// Calculate distance between 2 sets of longitude/latitude coordinates
// Takes two sets of coordinates in decimal longitude and latitude format and returns the distance in miles.
// php, distance, coordinates, longitude, latitude

// Oelwein, IA
$lat1 = 42.6733171;
$lon1 = -91.9135036;

// Independence, IA
$lat2 = 42.4685978;
$lon2 = -91.8893386;

$distance = (3958*3.1415926*sqrt(($lat2-$lat1)*($lat2-$lat1) + cos($lat2/57.29578)*cos($lat1/57.29578)*($lon2-$lon1)*($lon2-$lon1))/180);

echo 'The distance from '.$lat1.', '.$lon2.' to '.$lat2.', '.$lon2.' is '.$distance.' mi.';
?>