Error : mysqli::real_connect(): (08004/1040): Too many conne

我的网站有一些问题，我得到一个错误，太多的连接。

截图:http://pasteboard.co/Hz7QJQR.png

回溯说我的错误在我的__construct，模型函数list_slider和我的模型在get function:

这是我的控制器代码:

<?php 
if ( ! defined('BASEPATH')) exit('No direct script access allowed');
class Beranda extends CI_Controller {
    public function __construct()
    {
            parent::__construct();
            $this->load->helper(array('form', 'url', 'html'));
            $this->load->model(array('slider_model', 'slider_2_model', 'group_model', 'contact_model'));
    }
    public function index()
    {
            $data['slider_data'] = $this->slider_model->list_slider();
            $data['slider_2_data'] = $this->slider_2_model->list_slider();
            $data['group_data'] = $this->group_model->list_group();
            $data['contact_data'] = $this->contact_model->list_contact();
            $data['title'] = 'Kitchenware Equipments & Utensiles - norwinskitchenware.com';
            $this->load->view('fend/view_beranda', $data);
    }
}
?>

<<p>,这是我的模型strong>(更新):

<?php
    class Slider_model extends CI_Model {
        function list_slider()
        {
                $this->db->select('*');
                $this->db->from('slider');
                $query = $this->db->get();
                $this->db->close();
                return $query->result();
        }
     }
?>

我已经设置了'pconnect' => FALSE和mysql.allow_persistent = OFF

我该怎么办?

谢谢

public function __destruct() {  
    $this->db->close();  
}