codeigniter how to connect second database based on dynamic values

I want to import data from other database with dynamic connection

in codeigniter user input the database credential in the form and than I want to connect that database and import some data in the primary database. the question is how to set the second database connection with the dynamic values.

>Solution :

this is your first db connection from application/config/database.php

$db['default'] = array(
    'dsn'   => '',
    'hostname' => 'localhost',
    'username' => 'root',
    'password' => '',
    'database' => 'first_db',
    '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
);

and this is second db connection function from model or controller or helper your choice.

private function second_db(){
    return $db['second'] = array(
        'dsn'   => '',
        'hostname' => 'localhost',
        'username' => 'root',
        'password' => '',
        'database' => 'second_db',
        '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
    );
}
private function first_db(){
        return $db['second'] = array(
            'dsn'   => '',
            'hostname' => 'localhost',
            'username' => 'root',
            'password' => '',
            'database' => 'first_db',
            '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
        );
    }

if you set up your settings then you can switch your database with this code

$this->load->database(first_db(), TRUE);
$this->load->database(second_db(), TRUE);