php - 动态访问嵌套对象

Question

我正在构建一个可以利用多个网络服务进行地理编码(即 Google、Yahoo、Bing 等)的地理编码类。我正在尝试以一种可以轻松配置新 Web 服务的方式进行制作。大多数网络服务返回 XML/JSON。对于 PHP，我选择 XML 作为我的主要关注点。所有代码都已经到位，但现在 Google 例如返回以下 XML(转换为 simple_xml_element)

SimpleXMLElement Object
 (
[status] => OK
[result] => Array
    (
        [0] => SimpleXMLElement Object
            (
                [type] => postal_code
                [formatted_address] => 1010 Lausanne, Switzerland
                [address_component] => Array
                    (
                        [0] => SimpleXMLElement Object
                            (
                                [long_name] => 1010
                                [short_name] => 1010
                                [type] => postal_code
                            )

                        [1] => SimpleXMLElement Object
                            (
                                [long_name] => Lausanne
                                [short_name] => Lausanne
                                [type] => Array
                                    (
                                        [0] => locality
                                        [1] => political
                                    )

                            )

                        [2] => SimpleXMLElement Object
                            (
                                [long_name] => Vaud
                                [short_name] => VD
                                [type] => Array
                                    (
                                        [0] => administrative_area_level_1
                                        [1] => political
                                    )

                            )

                        [3] => SimpleXMLElement Object
                            (
                                [long_name] => Switzerland
                                [short_name] => CH
                                [type] => Array
                                    (
                                        [0] => country
                                        [1] => political
                                    )

                            )

                    )

                [geometry] => SimpleXMLElement Object
                    (
                        [location] => SimpleXMLElement Object
                            (
                                [lat] => 46.5376186
                                [lng] => 6.6539665
                            )

                        [location_type] => APPROXIMATE
                        [viewport] => SimpleXMLElement Object
                            (
                                [southwest] => SimpleXMLElement Object
                                    (
                                        [lat] => 46.5253574
                                        [lng] => 6.6384420
                                    )

                                [northeast] => SimpleXMLElement Object
                                    (
                                        [lat] => 46.5467887
                                        [lng] => 6.6745222
                                    )

                            )

                        [bounds] => SimpleXMLElement Object
                            (
                                [southwest] => SimpleXMLElement Object
                                    (
                                        [lat] => 46.5253574
                                        [lng] => 6.6384420
                                    )

                                [northeast] => SimpleXMLElement Object
                                    (
                                        [lat] => 46.5467887
                                        [lng] => 6.6745222
                                    )

                            )

                    )

            )
)

我需要的信息在 [location] 标签中，所以我尝试将路径存储在 var 中:

$lat_path = 'result[0]->geometry->location->lat;

然后尝试以这种方式访问​​值:

(suppose $xml is the object)
$xml->{$lat_path};

但这行不通。有什么方法可以动态或基于变量访问信息。我不想用 Google 特定代码破坏我的地理编码方法。

谢谢!

Answer 1

当你做的时候

$xml->{$lat_path};

PHP 将使用 $lat_path 中的任何内容作为变量名。它不会进入对象图或完全服从T_OBJECT_OPERATOR。它只会寻找一个属性

 'result[0]->geometry->location->lat;'

在 $xml 中。尝试运行此代码作为示例:

$obj = new StdClass;
$obj->{'result[0]->geometry->location->lat;'} = 1;
print_r($obj);

会输出

stdClass Object
(
    [result[0]->geometry->location->lat;] => 1
)

如您所见，它是一个单一属性，而不是嵌套对象图。

如评论中建议的那样，使用 XPath 或直接转到所需的值:

$xml->result[0]->geometry->location->lat;