XMLDiff\DOM can be use like this, for compare xml files changes. 

<?php
    

function getChangeElements($currentContent, $oldContent) {
        try {
            $currentDoc = new DOMDocument();
            $currentDoc->loadXML($currentContent);

            $oldDoc = new DOMDocument();
            $oldDoc->loadXML($oldContent);
            $xmldiff = new XMLDiff\DOM();
            return $xmldiff->diff($oldDoc, $currentDoc);
        } catch (Exception $ex) {
            throw $ex;
        }
    }

getChangeElements('updated.xml', 'old.xml');

?>