Description:
------------
Extended DOMDocument will change to unextended DOMDocument on context change


Test script:
---------------
<?php

class Document extends DOMDocument {
}

function foo() {
    $document = new Document();
    $element  = $document->appendChild($document->createElement('div'));
    var_dump($element->ownerDocument instanceOf Document);
    return $element;
}

$element = foo();
var_dump($element->ownerDocument instanceOf Document);


Expected result:
----------------
bool(true)
bool(true)


Actual result:
--------------
bool(true)
bool(false)