計算經緯度距離

//計算經緯度距離  km機關
    public function getDistance($lat1, $lng1, $lat2, $lng2)
    {
        $earthRadius = 6367; //地區半徑6367km
        $lat1 = ($lat1 * pi()) / 180;
        $lng1 = ($lng1 * pi()) / 180;
        $lat2 = ($lat2 * pi()) / 180;
        $lng2 = ($lng2 * pi()) / 180;
        $calcLongitude      = $lng2 - $lng1;
        $calcLatitude       = $lat2 - $lat1;
        $stepOne            = pow(sin($calcLatitude / 2), 2) + cos($lat1) * cos($lat2) * pow(sin($calcLongitude / 2), 2);
        $stepTwo            = 2 * asin(min(1, sqrt($stepOne)));
        $calculatedDistance = $earthRadius * $stepTwo;
        return round($calculatedDistance, 1);
    }