PHP XML DOM

The built-in DOM parser makes it possible to process XML documents in PHP.


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What is DOM?
The W3C DOM provides a standard set of objects for HTML and XML documents, and a standard interface for accessing and manipulating them.

The W3C DOM is separated into different parts (Core, XML, and HTML) and different levels (DOM Level 1/2/3):

* Core DOM - defines a standard set of objects for any structured document
* XML DOM - defines a standard set of objects for XML documents
* HTML DOM - defines a standard set of objects for HTML documents

If you want to learn more about the XML DOM, please visit our XML DOM tutorial.


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XML Parsing
To read and update - create and manipulate - an XML document, you will need an XML parser.

There are two basic types of XML parsers:

Tree-based parser: This parser transforms an XML document into a tree structure. It analyzes the whole document, and provides access to the tree elements
Event-based parser: Views an XML document as a series of events. When a specific event occurs, it calls a function to handle it
The DOM parser is an tree-based parser.

Look at the following XML document fraction:


Jani

The XML DOM sees the XML above as a tree structure:

Level 1: XML Document
Level 2: Root element:
Level 3: Text element: "Jani"

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Installation
The DOM XML parser functions are part of the PHP core. There is no installation needed to use these functions.


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An XML File
The XML file below will be used in our example:



Tove
Jani
Reminder
Don't forget me this weekend!



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Load and Output XML
We want to initialize the XML parser, load the xml, and output it:

Example
$xmlDoc = new DOMDocument();
$xmlDoc->load("note.xml");

print $xmlDoc->saveXML();
?>

The output of the code above will be:

Tove Jani Reminder Don't forget me this weekend!

If you select "View source" in the browser window, you will see the following HTML:



Tove
Jani
Reminder
Don't forget me this weekend!


The example above creates a DOMDocument-Object and loads the XML from "note.xml" into it.

Then the saveXML() function to puts the internal XML document into a string, so that we can print it.


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Looping through XML
We want to initialize the XML parser, load the XML, and loop through all elements of the element:

Example
$xmlDoc = new DOMDocument();
$xmlDoc->load("note.xml");$x = $xmlDoc->documentElement;
foreach ($x->childNodes AS $item)
{
print $item->nodeName . " = " . $item->nodeValue . "
";
}
?>

The output of the code above will be:

#text =
to = Tove
#text =
from = Jani
#text =
heading = Reminder
#text =
body = Don't forget me this weekend!
#text =

In the example above you see that there are empty text nodes between each element.

When XML generates, it often contains white-spaces between the nodes. The XML DOM parser treats these as ordinary elements, and if you are not aware of them, they sometimes cause problems.