Codeigniter : calling a method of one controller from other

Very simple way in codeigniter to call a method of one controller to other controller

1. Controller A 
   class A extends CI_Controller {

    public function __construct()
    {
        parent::__construct();
    }
    function custom_a()
    {
    }
}

2. Controller B 

   class B extends CI_Controller {

    public function __construct()
    {
        parent::__construct();
    }
    function custom_b()
    {
            require_once(APPPATH.'controllers/a.php'); //include controller
            $aObj = new a();  //create object 
            $aObj->custom_a(); //call function
    }
}

I agree that the way to do is to redirect to the new controller in usual cases.

I came across a use case where I needed to display the same page to 2 different kind of users (backend user previewing the page of a frontend user) so in my opinion what I needed was genuinely to call the frontend controller from the backend controller.

I solved the problem by making the frontend method static and wrapping it in another method. Hope it helps!

//==========
// Frontend
//==========
function profile()
{
   //Access check

   //Get profile id
   $id = get_user_id();

   return self::_profile($id);
}

static function _profile($id)
{
   $CI = &get_instance();
   //Prepare page
   //Load view
}

//==========
// Backend
//==========
function preview_profile($id)
{
   $this->load->file('controllers/frontend.php', false);

   Frontend::_profile($id);
}

This is not supported behavior of the MVC System. If you want to execute an action of another controller you just redirect the user to the page you want (i.e. the controller function that consumes the url).

If you want common functionality, you should build a library to be used in the two different controllers.

I can only assume you want to build up your site a bit modular. (I.e. re-use the output of one controller method in other controller methods.) There's some plugins / extensions for CI that help you build like that. However, the simplest way is to use a library to build up common "controls" (i.e. load the model, render the view into a string). Then you can return that string and pass it along to the other controller's view.

You can load into a string by adding true at the end of the view call:

$string_view = $this->load->view('someview', array('data'=>'stuff'), true);

test.php Controller File :

Class Test {
 function demo() {
  echo "Hello";
 }
}

test1.php Controller File :

Class Test1 {
 function demo2() {
  require('test.php');
  $test = new Test();
  $test->demo();
 }
}