Cannot convert this php array into xml

I am using cakephp v2.5. I would like to convert an array into xml. The array looks like this;

$Items = array(
    (int) 0 => array(
        'Item' => array(
            'id' => '2'
        )
    ),
    (int) 1 => array(
        'Item' => array(
            'id' => '4'
        )
    )
)

To convert this array to xml, the following php code was run;

$xmlObject = Xml::fromArray(array('response' => $Items ));
echo $xmlObject->asXML();  

Unfortunately, the following error was encountered;

Warning (2): SimpleXMLElement::__construct(): Entity: line 3: parser error : Extra content at the end of the document [CORE\Cake\Utility\Xml.php, line 221]

How can this array be converted into xml in php?