请求参数看这里

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<xml>
    <sign>1C8044E82B156A8B8A27791F8CCF902FA977B18E200760798B2195DB38B8EF89</sign>
    <nonce_str>o23QAakFrnwwf4sytZwDIOIKDFJTfwq9</nonce_str>
    <out_trade_no>68acd51be578455a87705c0288e72dfa</out_trade_no>
    <mch_id>15159149xx</mch_id>
    <sign_type>HMAC-SHA256</sign_type>
    <appid>wxe14682da9dba83xx</appid>
</xml>

返回的XML也很糟糕

<xml><return_code><![CDATA[FAIL]]></return_code>
<return_msg><![CDATA[缺少参数]]></return_msg>
</xml>