DOMXML question

What is the type of array returned by child_nodes()? I have an XML doc parsed into a DOM structure by $docnode = domxml_open_file("blah") then I get root by $root = $docnode->document_element(); then I get the first node $f_child = $root->first_child(); and then I want to get an array of all the children of f_child, like this $children = $f_child->child_nodes(); presumably it should give me an array of dom_nodes, and I should be able to perform actions with those, e.g. $children[0]->node_type(); or something similar, however, I get <b>Fatal error</b>: Call to a member function on a non-object in Am I missing something here?