The DOMXPath object doesn't create a reference to the document. If you load a new xml using either load, loadXML or loadHTML functions the DOMXPath object will still query and evaluate over the source in the DOMDocument when it was created.
Creates a new DOMXPath object.
document
The DOMDocument associated with the DOMXPath.
registerNodeNS
Whether to automatically register the in-scope namespace prefixes of the context node to the DOMXPath object. This can be used to avoid needing to call DOMXPath::registerNamespace() manually for each in-scope namespaces. When a namespace prefix conflict exists, only the nearest descendant namespace prefix is registered.
The DOMXPath object doesn't create a reference to the document. If you load a new xml using either load, loadXML or loadHTML functions the DOMXPath object will still query and evaluate over the source in the DOMDocument when it was created.