问未定义数组索引: access_token 显示错误？

//有code 获取token 和 用户信息
    	if(input('get.code')){
    		$code = input('get.code');
          	$redirectUrl = base64_decode($this->request->param('host'));

    		//获取token
    		$_token = $WeChat->get_access_token($code);
			//print_r($_token);exit;
    		//获取用户信息,记入cookie
    		$_user = $WeChat->get_user_info($_token['access_token'],$_token['openid']);
    		
    		cookie(['prefix' => '', 'expire' => 60*60*24]);
    		cookie('wx_info',$_user);
    		// cookie('wx_openid',$_user['openid']);
    		// cookie('wx_nickname',$_user['nickname']);
    		// cookie('wx_sex',$_user['sex']);
    		// cookie('wx_city',$_user['city']);
    		// cookie('wx_province',$_user['province']);
    		// cookie('wx_country',$_user['country']);