title: What is the relation between PHP and XML?
body: <p>I'm learning about PHP and web coding. <br>
  Specifically, the PHP book I'm using that covers PHP 5.3 (by Matt Doyle and published by Wrox), says: </p>
  
  <blockquote>
    <p>XML ... lets you create text documents that can hold  data in a structured way...<br>
    XML isn't really a language but rather a sepcification for creating your own markup languages...</p>
  </blockquote>
  
  <p>Wikipedia says of XML:</p>
  
  <blockquote>
    <p>As of 2009, hundreds of XML-based languages have been developed,[8] including RSS, Atom, SOAP, and XHTML. XML-based formats have become the default for many office-productivity tools, including Microsoft Office (Office Open XML), OpenOffice.org and LibreOffice (OpenDocument), and Apple's iWork.[9] XML has also been employed as the base language for communication protocols, such as XMPP.</p>
  </blockquote>
  
  <p>It sounds like XML is more like a protocol, a standard for allowing compuers to communicate and share information.</p>
  
  <p>So XML is like a grammar I can use to create a markup language, but the language I create only formats data?</p>
  
  <p>I want help defining  the relationship between PHP and XML.
  When during the processesing of PHP and HTML does XML get parsed?</p>