Over the last little while I've come across quite a few XML feed generators written in PHP, with varying degrees of 'correctness'. Even though generating XML should be very simple, there's still quite a bit of pitfalls I feel every PHP or (insert your language)-developer should know about.

His suggestions for better XML include:

• You are better off using an XML library (like xmlwriter)
• Understand Unicode
• CDATA is never a solution
• Be verbose
• Be careful with entities

They jump right in and show it in action by creating a simple RSS document with one element inside. A call to the flush() method on your XMLWriter object is all it takes to output the XML.

They also change things up and bit and swap out the procedural code for a more object-oriented approach with a constructor that sets up the object and adds in some of the common RSS information. Their addItem() method is called to add in a sample item (in this case, an entry for a CD player product) and _endRSS() closes things off and runs that flush() to send it all back out.

You can find out more about XMLWriter (and its sister, XMLReader) in the PHP manual.

• the DOM functionality (replacing DOM XML, ext/dom)
• SimpleXML
• XMLReader (replacing the ext/xml extension)
• XMLWriter
• XSL

Things are a bit different using XML in PHP 5. In a similar scenario, you could use one of the new native extensions, like DOM or SimpleXML, to manipulate the XML data tree. This tree can then be passed directly to and used by the XSL extension without incurring any additional overhead. There is no serialization nor copying involved; ext/xsl is able to work directly with the XML tree it is given, resulting in a significant improvement in use of system resources as compared to coding a similar task in PHP 4. So now that you have an idea why XML support got a face lift, you might like to know about the different tools available to you.

This is the XMLWriter extension. It wraps the libxml xmlWriter API.

This extension represents a writer that provides a non-cached, forward-only means of generating streams or files containing XML data. This extension can be used in an object oriented style or a procedural one. Every method documented describes the alternative procedural call.

The updated documentation cn be found here.

XMLWriter is finally bundled in php5. It will available and enabled by default in the next PHP release (5.1.2).

With XMLReader, XMLWriter is a really nice addition to the xml extensions.

The XMLWriter extension provides fast, non-cached, forward-only means of generating streams or files containing XML data. ]]> Wed, 07 Dec 2005 07:35:02 -0600