选定节点内的 SimpleXML xpath [英] SimpleXML xpath within selected node

问题描述

我有以下 XML 文件

I have the following XML file

<Item> 
  <name>...</name>
  <id>...</id>   
  <ImageSets>    
    <ImageSet Category="variant">
      <SwatchImage>
        <URL>...</URL>
        <Height Units="pixels"></Height>
        <Width Units="pixels"></Width>
      </SwatchImage>
      <SmallImage>
        <URL>...</URL>
        <Height Units="pixels"></Height>
        <Width Units="pixels"></Width>
      </SmallImage>
    </ImageSet>

    <ImageSet Category="primary">
      <SwatchImage>
        <URL>...</URL>
        <Height Units="pixels"></Height>
        <Width Units="pixels"></Width>
      </SwatchImage>
      <SmallImage>
        <URL>...</URL>
        <Height Units="pixels"></Height>
        <Width Units="pixels"></Width>
      </SmallImage>
    </ImageSet>
  </ImageSets>
</Item>

<Item>....</Item>

然后我使用 PHP 遍历文件中的 Item 节点.

Then I use PHP to iterate through Item nodes within file.

foreach ($Xml as $item){
    $name = $item->name;
    $ID = $item->id;
};

等等.该代码可以完美地为每个项目提取名称和 ID.

And so on. The code works perfect extracting names and Id's for every item.

现在我的问题是提取 ImageSet Category='primary'->SmallImage->URL.ImageSet 节点不按任何特定顺序排列，因此有时主要"会在前，有时会是变体"，这就是为什么 $item->ImageSets->ImageSet[1] 不是解决方案的原因

Now my problem is to extract ImageSet Category='primary'->SmallImage->URL. ImageSet nodes do not go in any particular order, so sometimes 'primary' will be first, sometimes 'variant', that's why $item->ImageSets->ImageSet[1] is not a solution

所以在我的主要 foreach 循环中，我尝试使用 xpath 如下:

So within my main foreach loop I've tried using xpath as follows:

$src='';    
foreach ($item->ImageSets->xpath('//ImageSet[@Category="primary"]') as $img){
    $src = $img->MediumImage->URL;
};

绝对没有运气.

任何想法将不胜感激.

推荐答案

您在 XPath 表达式中有错误.如果表达式以 / 开头，则它是相对于文档本身的.您希望它相对于当前节点.这意味着您有两种可能的解决方案

You have an error in the XPath expression. If the expression starts with an / it is relative to the document itself. You want it relative to the current node. This means you have two possible solutions

这将扩展为 child::ImageSet.它获取作为上下文节点的直接子节点的 ImageSet 元素节点.

This expands to child::ImageSet. It fetches the ImageSet element nodes that are direct children of the context node.

扩展并标准化为 descendant::ImageSet.它获取当前上下文中的任何 ImageSet，即使它不是直接子元素.. 代表当前节点，// 将轴更改为后代.

Expands and normalizes to descendant::ImageSet. It fetches any ImageSet inside the current context, even if it is not a direct child. The . represents the current node and // changes the axis to descendants.

这篇关于选定节点内的 SimpleXML xpath的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！