How to extend controller?

[eluser]shinokada[/eluser]
I created a Admin_Controller.php in application/libraries

However I am getting an error.
Could anyone point out what I am doing wrong please?

Thanks in advance.

Fatal error: Class 'Admin_Controller' not found in C:\xampp\htdocs\........

Code:

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class Admin_Controller extends Controller {
    function Admin_Controller()
    {
        parent::Controller();
        
    session_start();
    
    if (!isset($_SESSION['userid']) || $_SESSION['userid'] < 1){
    $this->session->set_flashdata('error',"You must log in!");  
        redirect('welcome/verify','refresh');
    }
    

    }
}

Now I want to use it in controllers/dashboard.php

Code:

<?php

class Dashboard extends Admin_Controller {
  function Dashboard(){
    parent::Admin_Controller();
    
  }
  

  function index(){    
    $data['title'] = "Dashboard Home";
    $data['main'] = 'admin_home';
    $data['messages'] =$this->MMessages-> getMessages();
    $this->load->vars($data);
    $this->load->view('dashboard');
  }

function logout(){
    unset($_SESSION['userid']);
    unset($_SESSION['username']);
    $this->session->set_flashdata('error',"You've been logged out!");
    redirect('welcome/verify','refresh');    
}

}
?>

[eluser]flaky[/eluser]

Code:

<?php

include_once APPPATH . "controllers/admin" . EXT;

class Dashboard extends Admin_Controller {

[eluser]rossmurphy[/eluser]
Have you got 'Admin' set up as your prefix in application/config.php. The default prefix is 'MY'.