The built-in DOM parser makes it possible to process XML documents in PHP.
W3C DOM provides a standard set of objects for HTML and XML documents, as well as a standard interface for accessing and manipulating these documents. W3C DOM is divided 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 - for XML documents Defining a standard set of objects* HTML DOM - Defining a standard set of objects for HTML documents To learn more about the XML DOM, visit our XML DOM tutorial.
To read and update - create and process - an XML document, you need an XML parser.
There are two basic types of XML parsers:
Tree-based parser: This parser converts XML documents into a tree structure. It analyzes the entire document and provides access to elements in the tree, such as the Document Object Model (DOM).
Event-based parser: Treats an XML document as a series of events. When a specific event occurs, the parser calls a function to handle it.
The DOM parser is a tree-based parser.
Please look at the following XML document fragment:
<?xml version="1.0" encoding="ISO-8859-1"?><from>Jani</from>
XML DOM treats the above XML as a tree structure:
Level 1: XML document
Level 2: Root element: <from>
Level 3: Text element: "Jani"
The DOM XML parser function is an integral part of PHP core. No installation is required to use these functions.
The following XML file will be used in our example:
<?xml version="1.0" encoding="ISO-8859-1"?><note><to>Tove</to><from>Jani</from><heading>Reminder</heading><body>Don 't forget me this weekend!</body></note>
We need to initialize the XML parser, load the XML, and output it:
<?php$xmlDoc = new DOMDocument();$xmlDoc->load("note.xml");print $xmlDoc->saveXML();?>The above code will output:
ToveJaniReminder Don't forget me this weekend!
If you view the source code in a browser window, you'll see the following HTML:
<?xml version="1.0" encoding="ISO-8859-1"?><note><to>Tove</to><from>Jani</from><heading>Reminder</heading><body>Don 't forget me this weekend!</body></note>
The above example creates a DOMDocument-Object and loads the XML in "note.xml" into this document object.
The saveXML() function puts the internal XML document into a string so we can output it.
We want to initialize the XML parser, load the XML, and iterate through all elements of the <note> element:
<?php$xmlDoc = new DOMDocument();$xmlDoc->load("note.xml");$x = $xmlDoc->documentElement;foreach ($x->childNodes AS $item) { print $item-> nodeName . " = " . $item->nodeValue . "<br>"; }?>The above code will output:
#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 is generated, it usually contains whitespace between nodes. The XML DOM parser treats them as normal elements, which can sometimes cause problems if you don't pay attention to them.
To learn more about XML DOM, visit our XML DOM tutorial.