PHP - XML 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
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:
<?xml version="1.0" encoding="ISO-8859-1"?>
<from>Jani</from>
The XML DOM sees the XML above as a tree structure:
- Level 1: XML Document
- Level 2: Root element: <from>
- Level 3: Text element: "Jani"
We want to initialize the XML parser, load the xml, and output it:
Load and Output XML Example
<?php
$xmlDoc = new DOMDocument();
$xmlDoc->load("note.xml");
print $xmlDoc->saveXML();
?>
The output of the code above will be:
Chris Jhon Reminder Don't forget me this weekend!
If you select "View source" in the browser window, you will 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 example above creates a DOMDocument-Object and loads the XML from "note.xml" into it.
Then 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 loop through all elements of the
element:
Looping through XML Example
<?php
$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.
