if ( ! $this->conn_id)
    {
        log_message('error', 'Unable to connect to the database');

        if ($this->db_debug)
        {
            $this->display_error('db_unable_to_connect'); //< line 124
        }
        return FALSE;
    }

$db['default']['hostname'] = 'localhost';
$db['default']['username'] = 'root'; // i have set privileges on phpmyadmin (WAMP)
$db['default']['password'] = 'root'; //set the username and password into 'root'
$db['default']['database'] = 'qb_architectdb'; // the name of my database
$db['default']['dbdriver'] = 'mysql'; // i tried to change to 'mysqli' nothing happened