(PHP 5 >= 5.1.0)
XMLReader::isValid — Indicates if the parsed document is valid
Returns a boolean indicating if the document being parsed is currently valid.
Returns TRUE on success or FALSE on failure.
Example #1 Validating XML
<?php
$xml = XMLReader::open('test.xml');
// You must to use it
$xml->setParserProperty(XMLReader::VALIDATE, true);
var_dump($xml->isValid());
?>