Voodoo\Core\Helpers::calculateDistance PHP Method

    public static function calculateDistance($lat1, $lon1, $lat2, $lon2, $unit = "M")
    {
        $theta = $lon1 - $lon2;
        $dist = sin(deg2rad($lat1)) * sin(deg2rad($lat2)) + cos(deg2rad($lat1)) * cos(deg2rad($lat2)) * cos(deg2rad($theta));
        $dist = acos($dist);
        $dist = rad2deg($dist);
        $miles = $dist * 60 * 1.1515;
        $unit = strtoupper($unit);
        if ($unit == "K") {
            return $miles * 1.609344;
        } else {
            if ($unit == "N") {
                return $miles * 0.8683999999999999;
            } else {
                return $miles;
            }
        }
    }