overtrue/wechat 怎么对接微信 对话服务

对文档的代码调整了下，但没办法打印sendl输出内容，难道要采用ob？

<?php

namespace app\controller;
use support\Request;
use EasyWeChat\Factory;
use Symfony\Component\HttpFoundation\HeaderBag;
use Symfony\Component\HttpFoundation\Request as SymfonyRequest;

use app\BaseController;

class Wechat extends BaseController
{
    public function index(Request $request)
    {
        $config = [
            'app_id' => '',
            'secret' => '',
            'token' => '',
            'response_type' => 'array',
        ];

        $app = Factory::officialAccount($config);

        $symfony_request = new SymfonyRequest($request->get(), $request->post(), [], $request->cookie(), [], [], $request->rawBody());
        $symfony_request->headers = new HeaderBag($request->header());
        $app->rebind('request', $symfony_request);

        $app->server->push(function ($message) {
            return "您好！欢迎关注";
        });

        $response = $app->server->serve();

        return $response->send()->getContent();
      }

}