SimpleXMLElement errors. Trying to add XML after particular point

Question

I am trying to add a new node after in designmap.xml

The new node includes an src attribute that is customized by the array below.

$newStories = Array ( [0] => u102 [1] => u103 [2] => u107 [3] => u156  );

$designMap = simplexml_load_file('designmap.xml');

foreach ($newStories as $story) {
  $newStoryNode = '<idPkg:Story src="Stories/Story_' . $story . '.xml" />';
  $insert = new SimpleXMLElement($newStoryNode);
  $target = current($designMap->xpath('//idPkg:Story[last()]'));

  simplexml_insert_after($insert, $target);
}

function simplexml_insert_after(SimpleXMLElement $insert, SimpleXMLElement $target)
{
    $target_dom = dom_import_simplexml($target);
    $insert_dom = $target_dom->ownerDocument->importNode(dom_import_simplexml($insert), true);
    if ($target_dom->nextSibling) {
        return $target_dom->parentNode->insertBefore($insert_dom, $target_dom->nextSibling);
    } else {
        return $target_dom->parentNode->appendChild($insert_dom);
    }
}

$designMap->asXML('designmap.xml');

I get the following warnings for each of the looks:

1. SimpleXMLElement::__construct(): namespace error : Namespace prefix idPkg on Story is not defined
2. SimpleXMLElement::__construct(): u102.xml
3. SimpleXMLElement::__construct(): ^ in

Answer 1

$xpath->query("//idPkg:Story[last()]")

Not sure you need to embrace the first statement "//idPkg:Story"