客服消息接口中 发送图文消息 收到图文消息乱码，其他正常

public function sendcustommessage($datas,$access_token){
    $url = sprintf($this->apiconfig['custommsg'],$access_token);
    $data = json_encode($datas,JSON_UNESCAPED_UNICODE);
    $result = $this->https_post($url,$data);
    return $result;
}