Codeigniter & PHP - forcing a 404?

Question

In codeigniter, as you know, a page of the form: /class/function/ID, where class is the controller name, function is the method within the controller, and ID is

Answer 1

Create controller in your application/controllers folder.

class Error extends Controller
{
function error_404()
{
    $this->load->view('error');
}
}

Then in your application/library extend the Router class by creating application/libraries/MY_Router.php

class MY_Router extends CI_Router
{
private $error_controller = 'error';
private $error_method_404 = 'error_404';

function MY_Router()
{
    parent::CI_Router();
}

// this is just the same method as in Router.php, with show_404() replaced by $this->error_404();
function _validate_request($segments)
{
    // Does the requested controller exist in the root folder?
    if(file_exists(APPPATH.'controllers/'.$segments[0].EXT))
    {
        return $segments;
    }

    // Is the controller in a sub-folder?
    if(is_dir(APPPATH.'controllers/'.$segments[0]))
    {
        // Set the directory and remove it from the segment array
        $this->set_directory($segments[0]);
        $segments = array_slice($segments, 1);
        if(count($segments) > 0)
        {
            // Does the requested controller exist in the sub-folder?
            if(!file_exists(APPPATH.'controllers/'.$this->fetch_directory().$segments[0].EXT))
            {
                return $this->error_404();
            }
        }
        else
        {
            $this->set_class($this->default_controller);
            $this->set_method('index');
            // Does the default controller exist in the sub-folder?
            if(!file_exists(APPPATH.'controllers/'.$this->fetch_directory().$this->default_controller.EXT))
            {
                $this->directory = '';
                return array();
            }
        }
        return $segments;
    }
    // Can't find the requested controller...
    return $this->error_404();
}

function error_404()
{
    $segments = array();
    $segments[] = $this->error_controller;
    $segments[] = $this->error_method_404;
    return $segments;
}

function fetch_class()
{
    // if method doesn't exist in class, change
    // class to error and method to error_404
    $this->check_method();
    return $this->class;
}

function check_method()
{
    $class = $this->class;
    if (class_exists($class))
    {
        if ($class == 'doc')
        {
            return;
        }
        if (! in_array('_remap', array_map('strtolower', get_class_methods($class)))
            && ! in_array(strtolower($this->method), array_map('strtolower', get_class_methods($class))))
        {
            $this->class = $this->error_controller;
            $this->method = $this->error_method_404;
            include(APPPATH.'controllers/'.$this->fetch_directory().$this->error_controller.EXT);
        }
    }
}

}

If the page does not exist, it will be routed to error controller