saveXML() adds another XML reference

I need to remove the parent node <feed> from this XML file so that I can use xpath without conflicts.

<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://ift.tt/r5ut6F">
   <entry>
      <contentVersion>preview-1.0.0</contentVersion>
      <embeddability value="http://ift.tt/145SZ6Q" />
      <openAccess value="http://ift.tt/1Aq01QG" />
      <viewability value="http://ift.tt/145SYQo" />
      <creator>Scott Blackwood</creator>
      <date>2015-01-20</date>
      <description>They bind up the three teenage girls who are working the counter, set fire to the shop, and disappear.</description>
      <format>224 pages</format>
      <format>book</format>
      <identifier>Hbd5oAEACAAJ</identifier>
      <identifier>ISBN:031637380X</identifier>
      <identifier>ISBN:9780316373807</identifier>
      <language>en</language>
      <publisher>Little, Brown</publisher>
      <subject>Fiction</subject>
      <title>See How Small</title>
      <title>A Novel</title>
   </entry>
</feed>

I currently have this XML stored in the variable $xml via the following code:

$xml = file_get_contents(http://ift.tt/1Bv0SNQ);

Here is what I have tried, and it mostly works

$doc = new DOMDocument();
$doc->loadHTML($xml);

// Remove doctype node
$doc->doctype->parentNode->removeChild($doc->doctype);

// Remove feed element, preserving child nodes
$html = $doc->getElementsByTagName("feed")->item(0);
$fragment = $doc->createDocumentFragment();
while ($html->childNodes->length > 0) {
    $fragment->appendChild($html->childNodes->item(0));
}
$html->parentNode->replaceChild($fragment, $html);

// Output results
echo $doc->saveXML();

But, my resulting text messes up the XML shebang line at the top. (adds a line):

<?xml version="1.0" standalone="yes"?>
<?xml version='1.0' encoding='UTF-8'??> 

Anyone know how to prevent this?