SimpleXML and mixed, nested namespaces

I work with several third party marketplace APIs, one of which is Amazon's MWS API.
When processing their GetMatchingProductForId response I discovered that they sometimes namespace the XML nodes (with ns2).

PHP's SimpleXML doesn't allow access to namespaced nodes via the usual interface of $simpleXml->node but I found you can specify a namespace to the children() method like so:

$simpleXml
    ->children('ns2', true)
    ->namespacedNode

That works great but then I hit a problem. As I mentioned, Amazon namespace some of the nodes but not all and the node I was really after was not namespaced itself but was a child of a namespaced node. After I applied the code above I found that I couldn't access the child node:

$simpleXml
    ->children('ns2', true)
    ->namespacedNode
    ->nonNamespacedNode

I thought all was lost until I discovered you can reset SimpleXML's namespace filter back to none again with another call to children() so you can get at the non-namespaced child node:

$simpleXml
    ->children('ns2', true)
    ->namespacedNode
    ->children()
    ->nonNamespacedNode