If your expression returns a node set, you will get a DOMNodeList instead of a typed result. Instead, try modifying your expression from "//node[1]" to "string(//node[1])".
If your expression returns a node set, you will get a DOMNodeList instead of a typed result. Instead, try modifying your expression from "//node[1]" to "string(//node[1])".