database list

PHP Code:

        $this->load->dbutil();
        $dbs = $this->dbutil->list_databases();

        foreach ($dbs as $db)
        {
            if ($this->dbutil->database_exists($db))
            {
                   echo $db."<br>";
            }
        } 


I don't understand, but it list all databases that I have (all, not just which I use in my application).

How to list the databases defined in the database.php (only) ?

Thanks a lot !!