PHP Manual: Register extended class used to create base node type

Description

public bool DOMDocument::registerNodeClass ( string $baseclass , string $extendedclass )

This method allows you to register your own extended DOM class to be used afterward by the PHP DOM extension.

This method is not part of the DOM standard.

Parameters

baseclass: The DOM class that you want to extend. You can find a list of these classes in the chapter introduction.
extendedclass: Your extended class name. If NULL is provided, any previously registered class extending baseclass will be removed.

Return Values

Returns TRUE on success or FALSE on failure.

Changelog

Version	Description
5.2.2	Prior to 5.2.2, a previously registered `extendedclass` had to be unregistered before being able to register a new class extending the same `baseclass`.

Examples

Example #1 Adding a new method to DOMElement to ease our code


<?php

class myElement extends DOMElement {
   function appendElement($name) { 
      return $this->appendChild(new myElement($name));
   }
}

class myDocument extends DOMDocument {
   function setRoot($name) { 
      return $this->appendChild(new myElement($name));
   }
}

$doc = new myDocument();
$doc->registerNodeClass('DOMElement', 'myElement');

// From now on, adding an element to another costs only one method call ! 
$root = $doc->setRoot('root');
$child = $root->appendElement('child');
$child->setAttribute('foo', 'bar');

echo $doc->saveXML();

?>

The above example will output:

<?xml version="1.0"?>
<root><child foo="bar"/></root>

Example #2 Retrieving elements as custom class


<?php
class myElement extends DOMElement {
    public function __toString() {
        return $this->nodeValue;
    }
}

$doc = new DOMDocument;
$doc->loadXML("<root><element><child>text in child</child></element></root>");
$doc->registerNodeClass("DOMElement", "myElement");

$element = $doc->getElementsByTagName("child")->item(0);
var_dump(get_class($element));

// And take advantage of the __toString method..
echo $element;
?>

The above example will output:

string(9) "myElement"
text in child

Example #3 Retrieving owner document

When instantiating a custom DOMDocument the ownerDocument property will refer to the instantiated class, meaning there is no need (and in fact not possible) to use DOMDocument::registerNodeClass with DOMDocument


<?php
class myDOMDocument extends DOMDocument {
}

class myOtherDOMDocument extends DOMDocument {
}

// Create myDOMDocument with some XML
$doc = new myDOMDocument;
$doc->loadXML("<root><element><child>text in child</child></element></root>");

$child = $doc->getElementsByTagName("child")->item(0);

// The current owner of the node is myDOMDocument
var_dump(get_class($child->ownerDocument));

// Import a node from myDOMDocument
$newdoc = new myOtherDOMDocument;
$child = $newdoc->importNode($child);

// The new owner of the node has changed to myOtherDOMDocument
var_dump(get_class($child->ownerDocument));
?>

The above example will output:

string(13) "myDOMDocument"
string(18) "myOtherDOMDocument"