微信申请退款参数都是按照手册传的，证书也正确但是还是给返回了缺少参数 调用接口https://api.mch.weixin.qq.com/secapi/pay/refund 请求参数为： <xml>         <appid>             <![CDATA[wx7f2421541006**]]>         </appid>         <mch_id>1608****0</mch_id>         <nonce_str>             <![CDATA[iQ0ddQota9dfXEdHGwa5tD1NJqlzEtBs]]>         </nonce_str>         <op_user_id>8888</op_user_id>         <out_refund_no>             <![CDATA[T20210416153****588]]>         </out_refund_no>         <refund_fee>3</refund_fee>         <total_fee>3</total_fee>         <transaction_id>4200000992202104***82</transaction_id>         <reason>             <![CDATA[退回]]>         </reason>         <sing>             <![CDATA[CD028852F3D15F6CF45**5F855C41]]>         </sing>     </xml> 接口返回值为： <pre>Array (     [return_code] => FAIL     [return_msg] => 缺少参数 )