Configure database config from function

yes you can

in your database config file add as many configuration groups as the numbers of your databases:

PHP Code:

$db['a']['hostname'] = 'localhost';
$db['a']['username'] = 'user';
$db['a']['password'] = 'pw';
$db['a']['database'] = 'db1';
...

$db['b']['hostname'] = 'localhost';
$db['b']['username'] = 'user';
$db['b']['password'] = 'pw';
$db['b']['database'] = 'db2';
...

//set the default db
$active_group = 'a'; 


then on your model initialize a class variable:

PHP Code:

private $db_b; 


and, into the contructor, set it as follow

PHP Code:

__construct()
{
   ...
   $this->db_b = $this->load->database('b', TRUE); 
} 


now you are able to use the database b as usual:

PHP Code:

$this->db_b->query('YOUR QUERY'); 


and obviously the default one as follow:

PHP Code:

$this->db->query('YOUR QUERY'); 


Make sure to set the persistant connect to false

PHP Code:

$db['a']['pconnect'] = FALSE;
$db['b']['pconnect'] = FALSE; 


You don't understand - I know how to use multiple databases. I need to set config this config manualy, because I want to create installer for my APP