XML无法解析&如何解决

$str1 = "http://user.qzone.qq.com/1340477530#!app=2&pos=1300412602";
$xml = ''."\r\n";
$xml .= ''."\r\n";
$xml .= "\t".''.$str1.''."\r\n";
$xml .= ''."\r\n";
$sxe = new SimpleXMLElement($xml);
$sxe->asXML('test.xml');

arning: SimpleXMLElement::__construct() [simplexmlelement.--construct]: Entity: line 3: parser error : EntityRef: expecting ';' in C:\wamp\www\test\a.php on line 18
Warning: SimpleXMLElement::__construct() [simplexmlelement.--construct]: http://user.qzone.qq.com/1340477530#!app=2\&pos=1300412602