php基于百度地图封装的对象类实现计算地图上两点间的距离和地理编码

class GeoHelper
{
    /*
     * @param int $lat1
     * @param int $lon1
     * @param int $lat2
     * @param int $lon2
     * @param string $unit
     * @return
     */
    public function distance($lon1, $lat1, $lon2, $lat2, $unit = "K")
    {
        $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 * 0.8684);
            } else { //mi
                return $miles;
            }
    }
    /**
     *地理编码
     * @param string $address
     * @param string $apikey
     * @return array [1]:lat [0]:lng
     */
    public function getLatLng($address, $apikey)
    {
        $find = array("\\n", "\\r", " ");
        $replace = array("", "", "+");
        $address = str_replace($find, $replace, $address);
        $url = 'http://api.map.baidu.com/geocoding/v3/?address=' . $address . '&ak=' . $apikey . '&output=json';
        $res = json_decode(file_get_contents($url), true);
        //var_dump($res);
        $coordinates = [$res["result"]["location"]["lng"], $res["result"]["location"]["lat"]];
        if (!empty($coordinates)) {
            return $coordinates;
        } else {
            return "";
        }
    }
}

$obj = new GeoHelper();
$str = "宁波市鄞州区泰康中路558号";
$ak = "F552bedbee2ec8fa6bae7b7a0**";
$b = $obj->getLatLng($str, $ak);
var_dump($b);
$c = $obj->distance(121.554586, 29.813444, 121.554649, 29.81231, "K");
echo number_format($c, 2) . "千米";