动态访问嵌套对象

Question

我正在构建一个Geocoding类,它可以利用多个Web服务进行地理编码(即Google,Yahoo,Bing等).我试图以一种可以轻松配置新的Web服务的方式来实现它.大多数web服务返回XML/JSON ..对于PHP我选择XML作为我的主要焦点.所有代码都已到位,但现在Google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
                                    )

                            )

                    )

            )
)

我需要的信息是在[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​​该值:

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

但这不起作用.有什么方法可以动态或基于变量访问信息.我不想破坏我使用Google特定代码的Geocoding方法.

谢谢!

Answer 1

当你这样做时

$xml->{$lat_path};

PHP 将使用其中的任何内容$lat_path作为变量名。它不会进入对象图或T_OBJECT_OPERATOR根本不遵守。它只会寻找一个属性

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

在$xml。尝试运行此代码作为示例：

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

它将输出

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

正如您所看到的，它是一个单一属性，而不是嵌套对象图。

就像评论中建议的那样，要么使用 XPath 要么直接转到所需的值：

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