How can I change the name of an element in DOM?

Question

In PHP with DOM, I have a DomElement object which represents an <identity/> element.

I have one case where I need to change this so its element name is <person/>, but keep the same child elements and attributes.

What would be the simplest way of changing an element name of a DomElement and keeping its children and attributes?

Edit: I have just found a very similar question (though it doesn't have very good answers).

Answer 1

Could you use importNode() to copy the childNodes of your <identity> element to a newly created <person> element?

function changeName($node, $name) {
    $newnode = $node->ownerDocument->createElement($name);
    foreach ($node->childNodes as $child){
        $child = $node->ownerDocument->importNode($child, true);
        $newnode->appendChild($child, true);
    }
    foreach ($node->attributes as $attrName => $attrNode) {
        $newnode->setAttribute($attrName, $attrNode);
    }
    $newnode->ownerDocument->replaceChild($newnode, $node);
    return $newnode;
}

$domElement = changeName($domElement, 'person');

Perhaps something like that would work, or you could try using cloneChild().

Edit: Actually, I just realized that the original function would lose the placement of the node. As per the question thomasrutter linked to, replaceChild() should be used.

Answer 2

Thanks to your post, I could quickly solve the same issue for me. However, I had a DOM_NOT_FOUND exception. This is probably a PHP Version issue, since the original post is 5 years old.

According to the PHP Documentation (Feb 2014)

DOM_NOT_FOUND
  Raised if oldnode is not a child of this node. 

So, I have replaced

$newnode->ownerDocument->replaceChild($newnode, $node);

with

$node->parentNode->replaceChild($newnode, $node);

Here is the complete function (tested):

public static function changeTagName($node, $name) {
    $childnodes = array();
    foreach ($node->childNodes as $child){
        $childnodes[] = $child;
    }
    $newnode = $node->ownerDocument->createElement($name);
    foreach ($childnodes as $child){
        $child2 = $node->ownerDocument->importNode($child, true);
        $newnode->appendChild($child2);
    }
    foreach ($node->attributes as $attrName => $attrNode) {
        $attrName = $attrNode->nodeName;
        $attrValue = $attrNode->nodeValue;
        $newnode->setAttribute($attrName, $attrValue);
    }
    $node->parentNode->replaceChild($newnode, $node);
    return $newnode;
}

It is also worth mentioning that when you want to use this function, you should traverse the DOM Tree in reversed order as explained in other posts.

UPDATE: After months of using and updating to PHP Version 5.5.15 on windows, I had an error saying $attr could not be converted to a string. So I updated third for-each loop above.

Answer 3

NOTE: I tried Calvin's code and it sort of worked for me but not quite. If the tag I was replacing had nested tags, some child tags would sometimes get lost.

The reason is that childNodes is a live DOMNodeList of a node's children, and appendChild moves the nodes around in the DOM, thus affecting the list ordering. If you just do foreach on a childNodes the loop can skip some children.

My solution was to use a while loop. This way you don't have to copy any nodes to an array.

I have packaged everything in a convenient function that takes a string and returns a string and should work with utf-8. The following is tested in PHP 5.5.9.

function renameTags($html, $oldname, $name) {
    $dom = new DOMDocument( '1.0', 'utf-8' );
    $fragment = $dom->createDocumentFragment();
    if ( $fragment->appendXML( $html ) ) {
        $dom->appendChild( $fragment );

        $nodesToAlter = $dom->getElementsByTagName( $oldname );

        while ($nodesToAlter->length) {
            $node = $nodesToAlter->item(0);

            $newnode = $node->ownerDocument->createElement($name);

            while ($node->hasChildNodes()) {
                $child = $node->childNodes->item(0);
                $child = $node->ownerDocument->importNode($child, true);
                $newnode->appendChild($child);
            }
            foreach ($node->attributes as $attr) {
                $attrName = $attr->nodeName;
                $attrValue = $attr->nodeValue;
                $newnode->setAttribute($attrName, $attrValue);
            }
            $newnode->ownerDocument->replaceChild($newnode, $node);

        }
        return $dom->saveHTML();
    } else {
        //error
    }
}


$html = 'Testing <b foo="bar" baz="foo">nested tags in <i lol="cat"> html strings</i></b> and <b>stuff</b>';

echo renameTags($html, 'b', 'strong');

Prints:

Testing <strong foo="bar" baz="foo">nested tags in <i lol="cat"> html strings</i></strong> and <strong>stuff</strong>