Add a note about XMLReader::isValid() only checks for the current node, not the entire document and improve the comment in the example a little

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@333737 c90b9560-bf6c-de11-be94-00142212c4b1

reference/xmlreader/xmlreader/isvalid.xml

@@ -31,7 +31,8 @@
 <?php
 $xml = XMLReader::open('test.xml');
 
-// You must to use it
+// The validate parser option must be enabled for 
+// this method to work properly
 $xml->setParserProperty(XMLReader::VALIDATE, true);
 
 var_dump($xml->isValid());
@@ -41,6 +42,14 @@ var_dump($xml->isValid());
    </example>
   </para>
  </refsect1>
+ <refsect1 role="notes">
+  &reftitle.notes;
+  <note>
+   <simpara>
+    This checks the current node, not the entire document.
+   </simpara>
+  </note>
+ </refsect1>
  <refsect1 role="seealso">
   &reftitle.seealso;
   <para>