Altering value of DomDocument element/node

Question

I'm building an XML like:

<?xml ... ?>
<root>
    <elements>0</elements>
    <list>
        <element>test1</element>
        <element>test1</element>
        <element>test1</element>
    </list>
</root>

After appending all <element>s, I want to replace <elements>0</elements> by <elements>3</elements> for example.

I tried DOMNode::replaceChild, but it has no affect.

$numberOfElements = $xml->createElement('numberOfElements', '0');
$root->appendChild($numberOfElements);

/* append elements and count them */

$root->replaceChild($numberOfElements,
                    $xml->createElement('numberOfElements', $countElements)
               );

How to properly use replaceChild or is there a different way?

Answer 1

From the docs:

public DOMNode replaceChild ( DOMNode $newnode , DOMNode $oldnode )

This means that you must specify the new node first, then the node to be replaced. You have it the wrong way around.

EDIT: That said, why not do this?

$numberOfElements->nodeValue = $countElements;