Question

I want to call a function in a controller (say controller_a) from another controller (say controller_b)

Please help me ..

Answer 1

Shared controller functions should usually be in an extended controller class:

<?php
/**
 *  File: /application/core/MY_Controller.php
 */
class MY_Controller extends CI_Controller {

    /**
     * Prefix with an underscore if you don't want it
     * publicly available through URI-routing
     */
    public function _some_shared_method()
    {
        // some common operation here
    }

}

Then, make sure any controller that needs to use this function extends MY_Controller.