php 正则提取XML 指定内容方法？求大拿帮忙（史上最难）
有XML内容 

<?xml version="1.0" encoding="GBK"?>

<stream><MSGCODE>AAAAAAA</MSGCODE><MSGCN>交易成功！</MSGCN><B2CCERTNO>500415</B2CCERTNO><ORDERDATE>2013-11-21</ORDERDATE><ORDERTIME>09:52:23</ORDERTIME><ORDERNO>DGM20131121000009</ORDERNO><ORDERAMT>6.26</ORDERAMT><CURRID>01</CURRID><PAYAMT>6.26</PAYAMT><PAYNO>BC131121095428004271</PAYNO><ACCNO>6226********6770</ACCNO><ACCTYPE>01</ACCTYPE><PBCSTNAME>测试</PBCSTNAME><ACCHASH>fSSczJM0fims1Xpmrvi2pnBtrr4=</ACCHASH></stream>

求使用PHP 提取出<MSGCODE>AAAAAAA</MSGCODE> 和 <ORDERNO>DGM20131121000009</ORDERNO> 中的 “AAAAAA"和 ”DGM20131121000009“ 可以使用正则进行匹配
------解决方案--------------------

$string = <<<XML

<?xml version="1.0" encoding="utf-8"?>

<stream><MSGCODE>AAAAAAA</MSGCODE><MSGCN>交易成功！</MSGCN><B2CCERTNO>500415</B2CCERTNO><ORDERDATE>2013-11-21</ORDERDATE><ORDERTIME>09:52:23</ORDERTIME><ORDERNO>DGM20131121000009</ORDERNO><ORDERAMT>6.26</ORDERAMT><CURRID>01</CURRID><PAYAMT>6.26</PAYAMT><PAYNO>BC131121095428004271</PAYNO><ACCNO>6226********6770</ACCNO><ACCTYPE>01</ACCTYPE><PBCSTNAME>测试</PBCSTNAME><ACCHASH>fSSczJM0fims1Xpmrvi2pnBtrr4=</ACCHASH></stream>

XML;



preg_match_all('#<(MSGCODE
------解决方案--------------------
ORDERNO)>(.+)</\1#s',$string,$m);

print_r($m);