$data = file_get_contents('xml-file.xml');
$doc = new DOMDocument();
@$doc->loadHTML($data);
$elements = $doc->getElementsByTagName('item');
$url = $elements->item(0)->getElementsByTagName('feedburner:origLink')->item(0)->nodeValue;
一方、タイトル、GUID、説明作業、理由がわかりません
$title = $elements->item(0)->getElementsByTagName('title')->item(0)->nodeValue;