phpeveryday.com

When we talk about WDDX document, we must talk about WDDX Packets. WDDX use packets to exchange data. Packets are simple XML documents passing data in WDDX format. Look following anatomy:

This is anatomy of WDDX without notes or comments:

<wddxPacket version='1.0'>
  <header />
  <data>
    <!-- WDDX data -->
</wddxPacket>

This is anatomy of WDDX with notes or comments:

<wddxPacket version='1.0'>
  <header>
    <comment>
	  It contains a comment
	</comment>
  </header>
  <data>
    <!-- WDDX data -->
</wddxPacket>

You can build this structure manually using an extension such as DOM or XMLWriter. But, PHP have wddx extension. So, you don't need much effort to create WDDX document.