PHP Manual: DOMDocument::validate

public function DOMDocument::validate(): bool

Validates the document based on its DTD.

You can also use the validateOnParse property of DOMDocument to make a DTD validation.

This function has no parameters.

Returns true on success or false on failure. If the document has no DTD attached, this method will return false.

Example #1 Example of DTD validation

<?php
$dom = new DOMDocument;
$dom->load('examples/book.xml');
if ($dom->validate()) {
    echo "This document is valid!\n";
}
?>

You can also validate your XML file while loading it:

<?php
$dom = new DOMDocument;
$dom->validateOnParse = true;
$dom->load('examples/book.xml');
?>

DOMDocument::validate