Code Igniter use muti database 1

Sometimes you might fall in a situation where you need multiple database connection at the same time. For example you might want to move (insert and delete) data from one database into another. This feature is very much useful for news sites as well due to maintain enourmass data.
Connection with multiple database with CI(Code Igniter) need a small trick. First you have to add lines of code in your configuration file in application/config/database.php. Add as much database configuration as you need
$active_group = "default";
$active_record = TRUE;
$db['default']['hostname'] = "localhost";
$db['default']['username'] = "root";
$db['default']['password'] = "";
$db['default']['database'] = "ci_practice";
$db['default']['dbdriver'] = "mysql";
$db['default']['dbprefix'] = "";
$db['default']['pconnect'] = TRUE;
$db['default']['db_debug'] = TRUE;
$db['default']['cache_on'] = FALSE;
$db['default']['cachedir'] = "";
$db['default']['char_set'] = "utf8";
$db['default']['dbcollat'] = "utf8_general_ci";


$db['second_db']['hostname'] = "localhost";
$db['second_db']['username'] = "root";
$db['second_db']['password'] = "";
$db['second_db']['database'] = "dev_job";
$db['second_db']['dbdriver'] = "mysql";
$db['second_db']['dbprefix'] = "";
$db['second_db']['pconnect'] = FALSE;
$db['second_db']['db_debug'] = TRUE;
$db['second_db']['cache_on'] = FALSE;
$db['second_db']['cachedir'] = "";
$db['second_db']['char_set'] = "utf8";
$db['second_db']['dbcollat'] = "utf8_general_ci";

So you have configured two different databases with their hostname, username and password. Moreover, you named them as default and second_db. In addition, you can choose any you like and as much database as you wish.
Now your class code application/controllers.test.php.
class Test extends Controller {
function __constructor()
{
parent::Controller();
$this->load->helper('url');
}
function duel_db2()
{
$this->load->model('test_model');
$user_data = $this->test_model->get_country(1);
print_r($user_data);

$user_data = $this->test_model->get_feedback(1);
print_r($user_data);
$this->load->database('default'); //Get Back into default.
}
}
finally your model (application/test_model.php) where from actually you connect multiple databases.
function get_country()
{
$DBOne = $this->load->database('second_db', TRUE);
$query = $DBOne
->from('countries')
->limit(10)
->where('id' , 10)
->get();
if ($query->num_rows() > 0)
{
$rows = $query->row_array();
return $rows;
}
return false;
}

function get_feedback($id)
{
$DBTwo = $this->load->database('default', TRUE);
$query = $DBTwo
->from('feedback')
->limit(10)
->where('id' , $id)
->get();
if ($query->num_rows() > 0)
{
$rows = $query->row_array();
return $rows;
}
return false;
}

Finally how it works? Lets say you call test controller as www.your-site.com/test/duel_db2
the duel_db2() function call test_model twice. first get_country(1). Lets have a closer look in this function. You connect default database by
$this->load->database('default');
and gets data from first database(ci_practice here). Second function call get_feedback() let the system able to connect with second database(dev_job here) by $DBTwo = $this->load->database('default', TRUE);
Keep in mind both of your connection is still alive
Enjoy with mutiple database connection simultaniouly with excellent framework (CI).