Multiple Database Connection

In the User Guide it says:
Connecting to Multiple Databases
If you need to connect to more than one database simultaneously you can do so as follows:
$DB1 = $this->load->database('group_one', TRUE);
$DB2 = $this->load->database('group_two', TRUE);

Is this to be placed in each model?

Please enlighten me with a more detailed explanation!!

Thanks in advance,
HEKuiper

It can be done in a number of different ways. The main thing to understand is that the var set by the return from $this->load->database('some_group', TRUE) has to be visible (in scope) in the model that uses it.

In other words, using this statement

PHP Code:

$DB2 = $this->load->database('db_config2', TRUE); 


The var $DB2 needs to be in scope to the model that uses it.

You could make $DB2 a public property of a Controller.

PHP Code:

Class Welcome extends CI_Controller
{
    public $DB2;

    function __construct()
    {
        parent::__construct();
        $this->DB2 = $this->load->database('db_config2', true);
        $this->load->model('othermodel');
    }

    public function index()
    {
        echo $this->othermodel->get_event();
    } 


And then use DB2 in "othermodel"

PHP Code:

class Othermodel extends CI_Model
{
   public function get_event()
   {

       return $this->DB2
           ->query("Select eventtitle from events where eventid = 20")
           ->row()
           ->eventtitle;
   }
} 


$this->DB2 could be used in any number of other models the controller requires. I don't intend to promote this approach as optimal or even truly desirable. Arguments against this approach are easily raised. Rather, the intent is only to demonstrate another way to make a connection visible to multiple models.  

Ultimately "where" you load additional databases probably depends more on how often you need more than one. That said, @Kaosweaver's answer is a great example of how easily create multiple connections in an arbitrary number of model classes.

Wow this is way less code!!  Thanks.

I have 3 websites and 4 databases - the 4th one I want to share commonalities with all 3 websites. 

Example: create 1 blog post and display it on 3 websites...  Taking DRY to a whole new level!!  :-)

Again, Thanks!!
HEKuiper