/**
* Perform an xpath query
*
* @param String $q query string containing xpath
* @param \DOMNode|null $ctx (optional) Context DOMNode
* @param boolean $registerNodeNS Register flag pass through
*
* @return \DOMNodeList
*/
public function query($q, \DOMNode $ctx = NULL, $registerNodeNS = TRUE)
{
if (is_null($this->xp)) {
$this->getDOMXPath();
}
return $this->xp->evaluate($q, $ctx, $registerNodeNS);
}
