【问题反馈】企业会话消息异步发送，传入的参数加入method字段

我用原生PHP写得接口，在使用

dingtalk.corp.message.corpconversation.asyncsend (企业会话消息异步发送) 接口时，明明已经传输了method参数，但是接口还是返回


21Missing methodhttp传入的参数加入method字段ish43gzd66fs


这样的错误，请问是我传输方式不对还是怎么回事啊？


下面我把源码粘上：
<?php

$access_token=file_get_contents('https://oapi.dingtalk.com/gettoken?corpid=dingefd0c3b****3e9c135c2f4657eb6378f&corpsecret=fEi6l6HuEvfTRZuur6****4s2zVVSuvGk9pBhSc8P5Yuy0MIizL_Zv3EXpQ6jT3');
$obj=json_decode($access_token);
//$access_token=$obj->access_token;
define(ACCESS_TOKEN,$obj->access_token);
$link=array("messageUrl"=>"http://wx.apkipa.cn/app/./index.php?i=3&c=entry&eid=201","picUrl"=>"http://b.hiphotos.baidu.com/image/pic/item/aa64034f78f0f736ce4ff5720055b319ebc4130b.jpg","title"=>"点进去试试","text"=>"事实就是是");
$timestamp=date("Y-m-d H:i:s");
$post_data=array("method"=>"dingtalk.corp.message.corpconversation.asyncsend","session"=>ACCESS_TOKEN,"format"=>"json","v"=>"2.0","timestamp"=>$timestamp,"touser"=>"06592423208****6","agentid"=>"12***238","msgtype"=>"link","msgcontent"=>$link);
//$post_data="method=dingtalk.corp.message.corpconversation.asyncsend&session".ACCESS_TOKEN;
echo $json=json_encode($post_data);
$url="https://eco.taobao.com/router/rest";
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
curl_setopt($ch, CURLOPT_POSTFIELDS,$post_data);
curl_setopt($ch, CURLOPT_RETURNTRANSFER,true);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);//这个是重点。
curl_setopt($ch, CURLOPT_HTTPHEADER, array(
    'Content-Type: application/json',
    'Content-Length: ' . strlen($json))
);
$result = curl_exec($ch);
if (curl_errno($ch)) {
    print curl_error($ch);
}
curl_close($ch);
echo $result;
?>