private function appendSpineElement(\DOMDocument $document, Spine $spine) { $node = $document->createElement('spine'); $node->setAttribute('toc', 'ncx'); foreach ($spine->all() as $item) { // $child = $document->createElementNS(NamespaceRegistry::NAMESPACE_DC, $item->name, $item->value); $child = $document->createElement('itemref'); $child->setAttribute('idref', $item->id); $node->appendChild($child); } return $node; }