PHP | DOMNode replaceChild() Function

The DOMNode::replaceChild() function is an inbuilt function in PHP which is used replace the old child node with the passed new node. Further, if the new node is already a child it will not be added the second time. If the replacement succeeds the old node is returned.

Syntax:

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

Parameters: This function accept two parameters as mentioned above and described below:

• $newnode: It specifies the new node.
• $oldnode: It specifies the old node.

Return Value: This function returns old node or FALSE if an error occur.

Exceptions: This function throws DOM_NO_MODIFICATION_ALLOWED_ERR, if this node is read-only or if the previous parent of the node being inserted is read-only, DOM_HIERARCHY_REQUEST_ERR, if this node is of a type that does not allow children of the type of the $newnode node, or if the node to put in is one of this node’s ancestors or this node itself, DOM_WRONG_DOCUMENT_ERR, if $newnode was created from a different document than the one that created this node, DOM_NOT_FOUND, if $oldnode is not a child of this node.

Below examples illustrate the DOMNode::replaceChild() function in PHP:

Program 1:

<?php

// Create a new DOMDocument instance
$document = new DOMDocument();

// Create a root element
$element = $document->appendChild(new DOMElement('root'));

// Create the text Node
$text1 = $document->createTextNode('Hello ! ');
$text2 = $document->createTextNode('Text to be replaced');
$text3 = $document->createTextNode('replaced');

// Append the nodes
$element->appendChild($text1);
$element->appendChild($text2);

// Replace the child
$element->replaceChild($text3, $text2);

// Render the output
echo $document->saveXML();

Output:

<?xml version="1.0"?>
<root>Hello ! replaced</root>

Example 2:

<?php

// Create a new DOMDocument instance
$document = new DOMDocument();

// Create a h1 element
$element = $document->appendChild(new DOMElement('h1'));

// Create the text Node
$text1 = $document->createTextNode('Geeksfor');
$text2 = $document->createTextNode('Text to be removed');
$text3 = $document->createTextNode('Geeks');

// Append the nodes
$element->appendChild($text1);
$element->appendChild($text2);

// Replace the child
$element->replaceChild($text3, $text2);

// Render the output
echo $document->saveXML();
?>

Output:

<?xml version="1.0"?>
<root>GeeksforGeeks</root>

Reference: https://www.php.net/manual/en/domnode.replacechild.php