How can I use XPath and DOM to replace a node/element in php?

Question

Say I have the following html

$html = '
<div class="website">
    <div>
        <div id="old_div">
            <p>some text</p>
            <p>some text</p>
            <p>some text</p>
            <p>some text</p>
            <div class="a class">
                <p>some text</p>
                <p>some text</p>
            </div>
        </div>
        <div id="another_div"></div>
    </div>
</div>
';

And I want to replace #old_div with the following:

$replacement = '<div id="new_div">this is new</div>';

To give an end result of:

$html = '
<div class="website">
        <div>
            <div id="new_div">this is new</div>
            <div id="another_div"></div>
        </div>
    </div>
';

Is there an easy cut-and-paste function for doing this with PHP?

Final working code thanks to all Gordon's help:

<?php

$html = <<< HTML
<div class="website">
    <div>
        <div id="old_div">
            <p>some text</p>
            <p>some text</p>
            <p>some text</p>
            <p>some text</p>
            <div class="a class">
                <p>some text</p>
                <p>some text</p>
            </div>
        </div>
        <div id="another_div"></div>
    </div>
</div>
HTML;

$dom = new DOMDocument;
$dom->loadXml($html); // use loadHTML if it's invalid XHTML

//create replacement
$replacement  = $dom->createDocumentFragment();
$replacement  ->appendXML('<div id="new_div">this is new</div>');

//make replacement
$xp = new DOMXPath($dom);
$oldNode = $xp->query('//div[@id="old_div"]')->item(0);
$oldNode->parentNode->replaceChild($replacement  , $oldNode);
//save html output
$new_html = $dom->saveXml($dom->documentElement);

echo $new_html;

?>

possible duplicate of Using DOMXPath to replace a node while maintaining its position ... — Gordon
– Gordon, Commented Jan 6, 2011 at 11:36
You can use XPath for selecting the target node to replace with a DOM method. Refrasing title. — user357812
– user357812, Commented Jan 6, 2011 at 12:11

Gordon · Accepted Answer · 2011-01-06 12:23:15Z

14

Since the answer in the linked duplicate is not that comprehensive, I'll give an example:

$dom = new DOMDocument;
$dom->loadXml($html); // use loadHTML if its invalid (X)HTML

// create the new element
$newNode = $dom->createElement('div', 'this is new');
$newNode->setAttribute('id', 'new_div');

// fetch and replace the old element
$oldNode = $dom->getElementById('old_div');
$oldNode->parentNode->replaceChild($newNode, $oldNode);

// print xml
echo $dom->saveXml($dom->documentElement);

Technically, you don't need XPath for this. However, it can happen that your version of libxml cannot do getElementById for non-validated documents (id attributes are special in XML). In that case, replace the call to getElementById with

$xp = new DOMXPath($dom);
$oldNode = $xp->query('//div[@id="old_div"]')->item(0);

Demo on codepad

To create a $newNode with child nodes without having to to create and append elements one by one, you can do

$newNode = $dom->createDocumentFragment();
$newNode->appendXML('
<div id="new_div">
    <p>some other text</p>
    <p>some other text</p>
    <p>some other text</p>
    <p>some other text</p>
</div>
');

edited Jan 6, 2011 at 12:23

answered Jan 6, 2011 at 11:41

Gordon

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5 Comments

Haroldo Over a year ago

@gordon

Catchable fatal error: Argument 2 passed to DOMNode::replaceChild() must be an instance of DOMNode, null given in C:\wamp\www\gv2010\user_area\replacement-test.php on line 24

?

Haroldo Over a year ago

@Gordon that's great. The reality behind my example is that $replacement html is much more complex than just a single node. Is there a way to use a string (heredoc) for the $newNode ?

Gordon Over a year ago

@Haroldo See update. Try de.php.net/manual/en/domdocumentfragment.appendxml.php

Haroldo Over a year ago

@Gordon - You sir, are an absolute legend.

Gordon Over a year ago

@Haroldo I'd love to believe that, but nah, I just know my way around DOM and some of it's quirks ;) You're welcome.

sshet · Accepted Answer · 2011-01-06 11:49:08Z

-7

use jquery hide() first to hide particular div and then use append to append new div

$('#div-id').remove();
$('$div-id').append(' <div id="new_div">this is new</div>');

edited Jan 6, 2011 at 11:49

answered Jan 6, 2011 at 11:43

sshet

1,1541 gold badge6 silver badges18 bronze badges

2 Comments

Peter Porfy Over a year ago

A question is about PHP (server side), not javascript (client side).

Haroldo Over a year ago

plus even if this was client side your solution is wrong because it is appending rather than replacing so would not preserve situe...

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