PHP弱语言又坑爹了:SimpleXML组件解析返回值的双重身份

function getDataForXML($res_data,$node)
{
 $xml = simplexml_load_string($res_data);
 $result = $xml->xpath($node);
while(list( , $node) = each($result))
 {
 return $node;
 }
}
//我只罗列了一个参数,实际的支付宝传入参数会很多,但结构都是这样的
$input = "<notify><out_trade_no>M2013012914195447849368424</out_trade_no><gmt_create>2013-01-29 14:20:11</gmt_create></notify>";
$test = getDataForXML($input,"/notify/out_trade_no");
echo $test."<br>";
$data = array(
 'tradeNo'=>$test,
);
$url = "http://blog.lizhigang.net/?".http_build_query($data);
echo $url;

M2013012914195447849368424
http://blog.lizhigang.net/?tradeNo%5B0%5D=M2013012914195447849368424

object(SimpleXMLElement)[2]string 'M2013012914195447849368424' (length=26)