Description:
------------
The formatOutput feature doesn' t work with documents, that use DomDocument::load() for creation. But it works with in memory DOM Documents.

Reproduce code:
---------------
$dom  = new DomDocument();
$file = "/path/to/file/dom.xml";
if (file_exists($file)) {
    $dom->load($file);
} else {
    $dom->appendChild(dom->createElement('foobar'));
}

printf("<pre>%s</pre>", htmlentities($dom->saveXML()));