codeigniter - php 新手 问题

    class Stock_model extends CI_Model{

        private $hsh;
        function __construct()
        {
            parent::__construct();
            $_ci = & get_instance();


            //$this->hsh = $_ci->load->database('hsh',TRUE);
            $hsh = $_ci->load->database('hsh',TRUE);
        }



        function  get_stock($goods_huo)
        {
            if(isset($goods_huo))
            {
                $hsh->where('item_huo',$goods_huo);
                $query =  $hsh->get('item_info');

                return $query->result_array();
                $query->free_result();

            }
        }
    }

<h4>A PHP Error was encountered</h4>
<p>Severity: Notice</p>
<p>Message:  Undefined variable: hsh</p>
<p>Filename: models/stock_model.php</p><p><span>立即学习</span>“<a href="https://pan.quark.cn/s/7fc7563c4182" style="text-decoration: underline !important; color: blue; font-weight: bolder;" rel="nofollow" target="_blank">PHP免费学习笔记（深入）</a>”；</p>
<p>Line Number: 22</p>
</div><br />
<b>Fatal error</b>:  Call to a member function where() on a non-object in <b>D:\htdocs\application\models\stock_model.php</b> on line <b>22</b><br />

    class Stock_model extends CI_Model{

        private $hsh;
        function __construct()
        {
            parent::__construct();
            $_ci = & get_instance();


            //$this->hsh = $_ci->load->database('hsh',TRUE);
            $hsh = $_ci->load->database('hsh',TRUE);
        }



        function  get_stock($goods_huo)
        {
            if(isset($goods_huo))
            {
                $hsh->where('item_huo',$goods_huo);
                $query =  $hsh->get('item_info');

                return $query->result_array();
                $query->free_result();

            }
        }
    }

<h4>A PHP Error was encountered</h4>
<p>Severity: Notice</p>
<p>Message:  Undefined variable: hsh</p>
<p>Filename: models/stock_model.php</p><p><span>立即学习</span>“<a href="https://pan.quark.cn/s/7fc7563c4182" style="text-decoration: underline !important; color: blue; font-weight: bolder;" rel="nofollow" target="_blank">PHP免费学习笔记（深入）</a>”；</p>
<p>Line Number: 22</p>
</div><br />
<b>Fatal error</b>:  Call to a member function where() on a non-object in <b>D:\htdocs\application\models\stock_model.php</b> on line <b>22</b><br />