PHP | DOMNode insertBefore() Function

The DOMNode::insertBefore() function is an inbuilt function in PHP which is used to insert a new node before a certain another node. Syntax:

DOMNode DOMNode::insertBefore( DOMNode $newNode, DOMNode $refNode )

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

• $newNode: It specifies the new node.
• $refNode (Optional): It specifies the reference node. If not supplied, newnode is appended to the children.

Return Value: This function returns the inserted node. Exceptions: This function throws DOM_NO_MODIFICATION_ALLOWED_ERR, if this node is readonly or if the previous parent of the node being inserted is readonly. 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 append 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 $refNode is not a child of this node. Below given programs illustrate the DOMNode::insertBefore() function in PHP: Program 1: php

<?php

// Create a new DOMDocument
$dom = new DOMDocument();

// Create a paragraph element
$p_element = $dom->createElement('p', 
      'This is the paragraph element!');

// Append the child
$dom->appendChild($p_element);

// Create a paragraph element
$h_element = $dom->createElement('h1', 
      'This is the heading element!');

// Insert heading before HTML
$dom->insertBefore($h_element, $p_element);

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

Output:

<?xml version="1.0"?>
<h1>This is the heading element!</h1>
<p>This is the paragraph element!</p>

Program 2: php

<?php

// Create a new DOMDocument
$dom = new DOMDocument();

// Create a paragraph element
$p_element = $dom->createElement('p', 
      'GeeksforGeeks, paragraph');

// Append the child
$dom->appendChild($p_element);

// Create a paragraph element
$h_element = $dom->createElement('h1',
      'GeeksforGeeks, heading');

// When second argument is not provided
// It will appended to the child
$dom->insertBefore($h_element);

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

Output:

<?xml version="1.0"?>
<p>GeeksforGeeks, paragraph</p>
<h1>GeeksforGeeks, heading</h1>

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