In most cases if you expect XML (or XHTML) as output you better use transformToXML() directly. You gain better control over xsl:output attributes, notably omit-xml-declaration.Instead of :$proc = new XSLTProcessor();$proc->importStylesheet($xsl);$dom = $proc->transformToDoc($xml);echo $dom->saveXML();do use : $proc = new XSLTProcessor();$proc->importStylesheet($xsl);$newXml = $proc->transformToXML($xml);echo $newXml;In the first case, <?xml version="1.0" encoding="utf-8"?> is added whatever you set the omit-xml-declaration while transformToXML() take the attribute into account.