一个VB+PHP+Nusoap的乱码问题

nusoap内的编码改为GB2312后response的xml：
HTTP/1.1 500 Internal Server Error
Date: Thu, 09 Sep 2004 04:15:03 GMT
Server: Apache/1.3.29 (Unix) PHP/4.3.4
X-Powered-By: PHP/4.3.4
Set-Cookie: PHPSESSID=b35fd0ac5381c048a5dc1a602fd66605; path=/
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Pragma: no-cache
X-Accelerated-By: PHPA/1.3.3r2
Status: 500 Internal Server Error
X-SOAP-Server: NuSOAP/0.6.6 (1.70)
Content-Length: 709
Connection: close
Content-Type: text/xml; charset=GB2312
Servererror in msg parsing:
XML error parsing SOAP payload on line 1: not well-formed (invalid token)