How to use the `xi:include` tag in XML files...

disclaimer.xml

<?xml version='1.0'?>
<disclaimer>
  <p>The opinions represented herein represent those of the individual
  and should not be interpreted as official policy endorsed by this
  organization.</p>
</disclaimer>

result.xml

<?xml version="1.0"?>
<document xmlns:xi="http://www.w3.org/2001/XInclude">
  <p>120 Mz is adequate for an average home user.</p>
  <disclaimer>
  <p>The opinions represented herein represent those of the individual
  and should not be interpreted as official policy endorsed by this
  organization.</p>
</disclaimer>
</document>

root.xml

<?xml version='1.0'?>
<document xmlns:xi="http://www.w3.org/2001/XInclude">
  <p>120 Mz is adequate for an average home user.</p>
  <xi:include href="disclaimer.xml"/>
</document>

xml.php

<?php

$doc = new DOMDocument();
$doc->load('root.xml');
$doc->xinclude();

echo $doc->saveXML();