SimpleXML xpath within selected node

Question

I have the following XML file

 
  ...
  ...   
      
    

        

Answer 1

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

ImageSet[@Category="primary"]

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

.//ImageSet[@Category="primary"]

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.

Answer 2

Realtive to your context node $item (I have no doubt there's why you need that context node ;-)) you're looking for ImageSet that a) is a child of ImageSets (which in turn is a direct child of your context node) and b) has the attribute Category with the value primary (which you have coded correctly)

<?php
$itemset = new SimpleXMLElement(data());
foreach ($itemset as $item) { // or something else - just some reason why you have to work with $item
    foreach ($item->xpath('ImageSets/ImageSet[@Category="primary"]') as $p) {
        echo $p->SwatchImage->URL;
    }
}


function data() {
    return <<< eox
<ItemSet>
    <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>primary swatch image 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>
</ItemSet>      
eox;
}