如何使用带有jsondecode的PHP获取json数据？

Question

我正在尝试在php中获取json数据

{
  "message":"otp verified",
  "type":"success"

 }

我尝试过以下代码来解析JSON数据

public function verify_register_otp(){

    $otp = $_POST['otp'];

    $api_key= $this->config->get('synicsys_working_key');
    $sender_id= $this->config->get('synicsys_sender_id');
    $mob_num= $this->config->get('synicsys_admin1');

    $sms = new Synicsys();
    $response= $sms->verify($mob_num,$otp,$api_key);


   $json = json_decode($response,true);

   return $json[1]->type; 

}

我遇到以下错误

{"message":"otp_not_verified","type":"error"}<b>Notice</b>: Trying to get property of non-object