Xmlreader + simpleelementxml: string could not be parsed as xml

Saya mencoba untuk memparse feed yang besar dari situs saya namun mendapat error "String could not be parsed as XML" dari hasil curl:

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, get_post_meta($post_id->ID, 'feed', true));
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 0);
curl_setopt($ch, CURLOPT_TIMEOUT, 30);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_ENCODING , 'gzip, deflate');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$rss = curl_exec($ch);
curl_close($ch);
$xml->xml($rss);

while ($xml->read()){
	if ($xml->nodeType == XMLReader::ELEMENT){
		$element = new SimpleXMLElement($xml->readOuterXML());

		foreach ($element as $channel){
		foreach ($channel->item as $item){

Mohon petunjuknya agar hasil curl bisa ter-parse ke dalam xml (masih tetap menggunakan SimpleXMLElement)