Unable to connect to your database server

<?php
defined('BASEPATH') OR exit('No direct script access allowed');
 
class Index extends CI_Controller {
 
 
 
    public function __construct()
    {
            parent::__construct();//ligne 10
        $this->load->helper('url');
         $this->load->model('Banner_model','banner');  
         $this->load->model('Category_model','category'); 
         $this->load->model('Produits_model','produit');
    }  

$active_group = 'default';
$query_builder = TRUE;
 
$db['default'] = array(
    'dsn'   => '',
    'hostname' => 'mondomaine.com',
    'username' => 'username',
    'password' => 'password',
    'database' => 'nomdatabase',
    'dbdriver' => 'mysqli',
    'dbprefix' => '',
    'pconnect' => FALSE,
    'db_debug' => (ENVIRONMENT !== 'production'),
    'cache_on' => FALSE,
    'cachedir' => '',
    'char_set' => 'utf8',
    'dbcollat' => 'utf8_general_ci',
    'swap_pre' => '',
    'encrypt' => FALSE,
    'compress' => FALSE,
    'stricton' => FALSE,
    'failover' => array(),
    'save_queries' => TRUE
);