• php
  • 1767
  • 20-3-2008
    • [L]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:
    <?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"
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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:
    <?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>

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    Load and Output XML
    We want to initialize the XML parser, load the xml, and output it:
    Example
    <?php
    
$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:
    <?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 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 <note> element:
    Example
    <?php
    
$xmlDoc = new DOMDocument();
    
$xmlDoc->load("note.xml");$x = $xmlDoc->documentElement;
    
foreach ($x->childNodes AS $item)
    
  {
    
  print $item->nodeName . " = " . $item->nodeValue . "<br />";
    
  }
    
?>

    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.[/L]
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