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.