(PHP 5 >= 5.1.0, PHP 7)
XMLReader::isValid — Indicates if the parsed document is valid
Returns a boolean indicating if the document being parsed is currently valid.
成功时返回 TRUE， 或者在失败时返回 FALSE。
Example #1 Validating XML
<?php
$xml = XMLReader::open('test.xml');
// The validate parser option must be enabled for
// this method to work properly
$xml->setParserProperty(XMLReader::VALIDATE, true);
var_dump($xml->isValid());
?>
Note: This checks the current node, not the entire document.