带有 Highcharts 的 codeigniter-数据不来控制器查看

Question

我尝试将 highcharts 库添加到我的 CI 项目中。所以我在我的控制器中尝试了 db query

<?php

defined('BASEPATH') OR exit('No direct script access allowed');

class ChartController extends CI_Controller {

  public function __construct() {

       parent::__construct();

       $this->load->database();

    } 

    public function index()

    {

        $query = $this->db->query("SELECT SUM(numberofclick) as count FROM demo_click 

            GROUP BY YEAR(created_at) ORDER BY created_at"); 

        $data['click'] = json_encode(array_column($query->result(), 'count'),JSON_NUMERIC_CHECK);

        $query = $this->db->query("SELECT SUM(numberofview) as count FROM demo_viewer 

            GROUP BY YEAR(created_at) ORDER BY created_at"); 

        $data['viewer'] = json_encode(array_column($query->result(), 'count'),JSON_NUMERIC_CHECK);

        $this->load->view('my_chart', $data);

    }

}

然后我尝试通过视图访问。我放置了以下代码来检查控制器的输出。

<?php

 echo var_dump($this->_ci_cached_vars);

?>

然后我得到，以下输出没有值。这是什么问题？

array (size=2)

  'click' => string '[]' (length=2)

  'viewer' => string '[]' (length=2)