DOMNode::insertBefore

(PHP 5, PHP 7)

DOMNode::insertBefore — Adds a new child before a reference node

Description

public DOMNode DOMNode::insertBefore ( DOMNode $newnode [, DOMNode $refnode ] )

This function inserts a new node right before the reference node. If you plan to do further modifications on the appended child you must use the returned node.

Parameters

newnode: The new node.
refnode: The reference node. If not supplied, newnode is appended to the children.

Return Values

The inserted node.

Errors/Exceptions

DOM_NO_MODIFICATION_ALLOWED_ERR: Raised if this node is readonly or if the previous parent of the node being inserted is readonly.
DOM_HIERARCHY_REQUEST_ERR: Raised 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: Raised if newnode was created from a different document than the one that created this node.
DOM_NOT_FOUND: Raised if refnode is not a child of this node.

User Contributed Notes

jg at handcode dot de

10 years ago


example to insert <newnode/> between <chid1/> and <child2/>

<?xml version="1.0" encoding="ISO-8859-1" ?>     
<root> 
  <parent> 
    <child nr="1"/> 
    <child nr="2"/> 
  </parent> 
</root> 

<?php 
 
$xml_src = 'test.xml'; 
 
// XPath-Querys 
$parent_path = "//parent"; 
$next_path = "//parent/child[@nr='2']"; 
 
// Create a new DOM document 
$dom = new DomDocument(); 
$dom->load($xml_src); 
 
// Find the parent node 
$xpath = new DomXPath($dom); 
 
// Find parent node 
$parent = $xpath->query($parent_path); 
 
// new node will be inserted before this node 
$next = $xpath->query($next_path); 
 
// Create the new element 
$element = $dom->createElement('newnode'); 
 
// Insert the new element 
$parent->item(0)->insertBefore($element, $next->item(0)); 
 
echo $dom->saveXML(); 
 
?>

jarry1250 at gmail dot com

11 months ago


Note that supplying the same node for $newnode and $refnode leads to an E_WARNING ("Couldn't add newnode as the previous sibling of refnode"). For example imagine one wanted to make $newnode the first child of its parent by doing:

<?php
$firstSibling = $newnode->parentNode->firstChild;
// Bad:
$newnode->parentNode->insertBefore( $newnode, $firstSibling );
?>

This would generate a warning if it already was the first child of its parent, since $newnode and $firstSibling are identical. Easy to work around though:

<?php
$firstSibling = $newnode->parentNode->firstChild;
// Better:
if( $newnode !== $firstSibling ) {
    $newnode->parentNode->insertBefore( $newnode, $firstSibling );
}
?>

Jerry Ellis

10 years ago


1st argument) a node to insert 
2nd argument) a reference node - this is the node that the new node will be inserted before

The trick to using this method is that the OBJECT on which you actually CALL the insertBefore() method is actually the PARENT node of the reference node!  

INCORRECT:
$DOMNode_refNode->insertBefore($DOMNode_newNode, $DOMNode_refNode); 

CORRECT:
$DOMNode_refNode->parentNode->insertBefore($DOMNode_newNode, $DOMNode_refNode);

justin at redwiredesign dot com

9 years ago


The previous example is incorrect, and causes a DOM_NOT_FOUND error, as the child nodes are not direct descendants of the root node.

Therefore, the line:

$parent_path = "/root";

needs to change to:

$parent_path = "/root/parent";

or 

$parent_path = "//parent";

for this example to work

DrTebi at Yahoo

8 years ago


Sorry, my previous posting worked only for the top node. Here the corrected version, which will work for any node:

XML
----
<?xml version="1.0"?>
<contacts>
  <person>Adam</person>
  <person>Eva</person>
  <person>Thomas</person>
</contacts>

PHP
---
<?php
// load XML, create XPath object
$xml = new DomDocument();
$xml->preserveWhitespace = false;
$xml->load('contacts.xml');
$xpath = new DOMXPath($xml);

// get node eva, which we will append to
$eva = $xpath->query('/contacts/person[.="Eva"]')->item(0);

// create node john
$john = $xml->createElement('person', 'John');

// insert john after eva
//   "in eva's parent node (=contacts) insert
//   john before eva's next node"
// this also works if eva would be the last node
$eva->parentNode->insertBefore($john, $eva->nextSibling);

// show result
header('Content-Type: text/plain');
print $xml->saveXML();
?>

Result
------
<?xml version="1.0"?>
<contacts>
  <person>Adam</person>
  <person>Eva</person><person>John</person>
  <person>Thomas</person>
</contacts>