How to Connect to Multiple Databases in CodeIgniter

Connecting to multiple databases is simpler in CodeIgniter. All you have to do is to establish a separate connection for each database you wish to work. Here I'll show you how to connect with two MySQL Databases.

1. Open the "application/config/database.php" file.

2. You can see a list of default connection settings provided. Now enter the hostname, username, password, database & database prefix (if any) you want to connect.

$db['default']['hostname'] = 'localhost';
$db['default']['username'] = 'mysql_username';
$db['default']['password'] = 'mysql_password';
$db['default']['database'] = 'employee';
$db['default']['dbdriver'] = 'mysql';
$db['default']['dbprefix'] = 'kms';
$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['default']['swap_pre'] = '';
$db['default']['autoinit'] = TRUE;
$db['default']['stricton'] = FALSE;

3. Make another copy of the connection settings with different name and provide the second database details you want to connect.

$db['ADMINDB']['hostname'] = 'localhost';
$db['ADMINDB']['username'] = 'mysql_username';
$db['ADMINDB']['password'] = 'mysql_password';
$db['ADMINDB']['database'] = 'admin';
$db['ADMINDB']['dbdriver'] = 'mysql';
$db['ADMINDB']['dbprefix'] = 'kms';
$db['ADMINDB']['pconnect'] = TRUE;
$db['ADMINDB']['db_debug'] = TRUE;
$db['ADMINDB']['cache_on'] = FALSE;
$db['ADMINDB']['cachedir'] = '';
$db['ADMINDB']['char_set'] = 'utf8';
$db['ADMINDB']['dbcollat'] = 'utf8_general_ci';
$db['ADMINDB']['swap_pre'] = '';
$db['ADMINDB']['autoinit'] = TRUE;
$db['ADMINDB']['stricton'] = FALSE;

4. Now you can access the databases like this,

//access default database
$this->load->database();
$query = $this->db->get('staff');
foreach ($query->result() as $row)
echo $row->name;

//access the second database
$admin_db= $this->load->database('ADMINDB', TRUE);
$query = $admin_db->get('members');
foreach ($query->result() as $row)
echo $row->role;

You can connect with two or more databases in CodeIgniter in the same way. Follow the same procedure if you want to connect to databases other than MySQL.

Source: kodingmadesimple