How to change root of a node with DOMDocument methods?

Question

How to only change root's tag name of a DOM node?

In the DOM-Document model we can not change the property documentElement of a DOMElement object, so, we need "rebuild" the node... But how to "rebuild" with childNodes property?

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NOTE: I can do this by converting to string with saveXML and cuting root by regular expressions... But it is a workaround, not a DOM-solution.

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Tried but not works, PHP examples

PHP example (not works, but WHY?):

Try-1

 // DOMElement::documentElement can not be changed, so... 

 function DomElement_renameRoot1($ele,$ROOTAG='newRoot') { 
    if (gettype($ele)=='object' && $ele->nodeType==XML_ELEMENT_NODE) {
   $doc = new DOMDocument();
   $eaux = $doc->createElement($ROOTAG); // DOMElement

       foreach ($ele->childNodes as $node)  
       if ($node->nodeType == 1)  // DOMElement 
               $eaux->appendChild($node);  // error!
       elseif ($node->nodeType == 3)  // DOMText
               $eaux->appendChild($node); // error!
       return $eaux;
    } else
        die("ERROR: invalid DOM object as input");
  }

The appendChild($node) cause an error:

 Fatal error: Uncaught exception 'DOMException' 
 with message 'Wrong Document Error'

Try-2

From @can suggestion (only pointing link) and my interpretation of the poor dom-domdocument-renamenode manual.

 function DomElement_renameRoot2($ele,$ROOTAG='newRoot') {
$ele->ownerDocument->renameNode($ele,null,"h1");
    return $ele;
 }

The renameNode() method caused an error,

Warning: DOMDocument::renameNode(): Not yet implemented

Try-3

From PHP manual, comment 1.

 function renameNode(DOMElement $node, $newName)
 {
     $newNode = $node->ownerDocument->createElement($newName);
     foreach ($node->attributes as $attribute)
        $newNode->setAttribute($attribute->nodeName, $attribute->nodeValue);
     while ($node->firstChild)
        $newNode->appendChild($node->firstChild); // changes firstChild to next!?
     $node->ownerDocument->replaceChild($newNode, $node); // changes $node?
     // not need return $newNode; 
 }

The replaceChild() method caused an error,

Fatal error: Uncaught exception 'DOMException' with message 'Not Found Error'

Answer 1

As this has not been really answered yet, the error you get about not found is because of a little error in the renameNode() function you've copied.

In a somewhat related question about renaming different elements in the DOM I've seen this problem as well and used an adoption of that function in my answer that does not have this error:

/**
 * Renames a node in a DOM Document.
 *
 * @param DOMElement $node
 * @param string     $name
 *
 * @return DOMNode
 */
function dom_rename_element(DOMElement $node, $name) {
    $renamed = $node->ownerDocument->createElement($name);

    foreach ($node->attributes as $attribute) {
        $renamed->setAttribute($attribute->nodeName, $attribute->nodeValue);
    }

    while ($node->firstChild) {
        $renamed->appendChild($node->firstChild);
    }

    return $node->parentNode->replaceChild($renamed, $node);
}

You might have spotted it in the last line of the function body: This is using ->parentNode instead of ->ownerDocument. As $node was not a child of the document, you did get the error. And it also was wrong to assume that it should be. Instead use the parent element to search for the child in there to replace it ;)

This has not been outlined in the PHP manual usernotes so far, however, if you did follow the link to the blog-post that originally suggested the renameNode() function you could find a comment below it offering this solution as well.

Anyway, my variant here uses a slightly different variable naming and is more distinct about the types. Like the example in the PHP manual it misses the variant that deals with namespace nodes. I'm not yet booked what would be best, e.g. creating an additional function dealing with it, taking over namespace from the node to rename or changing the namespace explicitly in a different function.