<?php 

function calculateDistance($latitude1, $longitude1, $latitude2, $longitude2) {
    $theta = $longitude1 - $longitude2;
    $distance = (sin(deg2rad($latitude1)) * sin(deg2rad($latitude2))) + (cos(deg2rad($latitude1)) * cos(deg2rad($latitude2)) * cos(deg2rad($theta)));
    $distance = acos($distance);
    $distance = rad2deg($distance);
    $distance = $distance * 60 * 1.1515;
    // Kilometers
    $distance = $distance * 1.609344;
    
    return $distance; 
}

?>

