Controller Problem

[eluser]BD-CI-Programmer[/eluser]
Dear All,
I am two controller like this

Code:

<?php
class Bangladesh extends Controller
{
    function Bangladesh ()
    {
        parent::Controller();
    }
function hello_bangladesh()
     {
// Code

     }

}
?>

And other

Code:

<?php
class World extends Controller
{
    function World()
    {
        parent::Controller();
    }
function hello_world()
     {
// Code

     }

}
?>

Now I want to call function hello_world in the hello_bangladesh function.

How it Possible...