Calculating distance between two geo-points.

distance.php

<?php
function distance($fromLat, $fromLon, $toLat, $toLon) {
    $radius   = 6378.1; // 3963.17 miles
    $dLat     = deg2rad($toLat - $fromLat);
    $dLon     = deg2rad($toLon - $fromLon);
    $tmp      = cos(deg2rad(($fromLat + $toLat) / 2)) * $dLon;
    $distance = $radius * sqrt($dLat * $dLat + $tmp * $tmp);
    return round($distance, 1);
}

echo distance(41.00518, 28.97702, 39.948701, 32.857361);
?>