<?php
function lat_long_dist_of_two_points($latitudeFrom, $longitudeFrom, $latitudeTo, $longitudeTo){ 
$pi = pi(); 
$x = sin($latitudeFrom * $pi/180) * 
sin($latitudeTo * $pi/180) + 
cos($latitudeFrom * $pi/180) * 
cos($latitudeTo * $pi/180) * 
cos(($longitudeTo * $pi/180) - ($longitudeFrom * $pi/180)); 
$x = atan((sqrt(1 - pow($x, 2))) / $x); 
return abs((1.852 * 60.0 * (($x/$pi) * 180)) / 1.609344); 
} 
// Distance from New York to London
echo lat_long_dist_of_two_points(40.7127, 74.0059, 51.5072, 0.1275).' mi'."\n"; 
?>