PHP xmlhttp编码问题？请看代码!

 <?php//Microsoft.XMLHTTP组件使用范例程序get.php
$url="http://bestrip.vicp.cc:352/ib_tranx_req.asp?uid=wz001&sessionid=dd8edd0ca3a54d3403c84929274771adtermid=&cmd=av&disp_special=1&disp_share=1&verify=0&start_city=SHA&arrive_city=PEK&date=2009-4-13";$xmlhttp = new COM("Microsoft.XMLHTTP") or die("无法创建Microsoft.XMLHTTP组件!");$xmlhttp->open("GET",$url,False, "", "");
$xmlhttp->setRequestHeader("content-Type","text/xml");$xmlhttp->send();
//header('Content-Type:text/html;charset=UTF-8');
$body=$xmlhttp->responseText;echo $body;?>通过查看源码怎么页面里面xml显示为：
<?xml version="1.0" encoding="GB2312"?>
<air_info ret_value="1" date="13APR(MON)" from="SHA" to="PEK" fromname="?????" toname="???????" Mileage="1178">
<airline line_number="CA1858" company="?????????" sc="SHA" sa="???????ac="PEK" aa="?????????stime="0755" atime="1020" airrax="50" fulerax="0" food="1" dfly="1" type="772" et="1"> 
<c b="F" d="???? p="1700" s="A"></c>
<c b="Y" d="???? p="1130" s="A"></c>
<c b="S" d="*δ?" p="0" s="A"></c>
</airline>
<airline line_number="*FM9891" company="?????????" sc="SHA" sa="???????ac="PEK" aa="?????????stime="0755" atime="1020" airrax="50" fulerax="0" food="1" dfly="1" type="772" et="1"> 
<c b="F" d="???? p="1700" s="A"></c>
<c b="Y" d="???? p="1130" s="A"></c>
怎么回事?我怎么处理这个编码的问题？