koseven/system/guide/kohana/tutorials/error-pages.md

Custom Error Pages

Custom error pages allow you to display a friendly error message to users, rather than the standard Kohana stack trace.

Prerequisites

1. You will need 'errors' => TRUE passed to [Kohana::init]. This will convert PHP-errors into exceptions which are easier to handle (The default value is TRUE).
2. Custom error pages will only be used to handle throw [HTTP_Exception]'s. If you simply set a status of, for example, 404 via [Respose::status] the custom page will not be used.

Extending the HTTP_Exception classes

Handling [HTTP_Exception]'s in Kohana has become easier with the changes introduced in 3.3.

For each [HTTP_Exception] class we can individually override the generation of the [Response] instance.

[!!] Note: We can also use HMVC to issue a sub-request to another page rather than generating the [Response] in the [HTTP_Exception] itself.

For example, to handle 404 pages we can do this in APPPATH/classes/HTTP/Exception/404.php:

class HTTP_Exception_404 extends Kohana_HTTP_Exception_404 {

    /**
     * Generate a Response for the 404 Exception.
     *
     * The user should be shown a nice 404 page.
     * 
     * @return Response
     */
    public function get_response()
    {
        $view = View::factory('errors/404');

        // Remembering that `$this` is an instance of HTTP_Exception_404
        $view->message = $this->getMessage();

        $response = Response::factory()
            ->status(404)
            ->body($view->render());

        return $response;
    }
}

Another example, this time to handle 401 Unauthorized errors (aka "Not Logged In") we can do this in APPPATH/classes/HTTP/Exception/401.php:

class HTTP_Exception_401 extends Kohana_HTTP_Exception_401 {

    /**
     * Generate a Response for the 401 Exception.
     * 
     * The user should be redirect to a login page.
     * 
     * @return Response
     */
    public function get_response()
    {
        $response = Response::factory()
            ->status(401)
            ->headers('Location', URL::site('account/login'));

        return $response;
    }
}

Finally, to override the default [Response] for all [HTTP_Exception]'s without a more specific override we can do this in APPPATH/classes/HTTP/Exception.php:

class HTTP_Exception extends Kohana_HTTP_Exception {

    /**
     * Generate a Response for all Exceptions without a more specific override
     * 
     * The user should see a nice error page, however, if we are in development
     * mode we should show the normal Kohana error page.
     * 
     * @return Response
     */
    public function get_response()
    {
        // Lets log the Exception, Just in case it's important!
        Kohana_Exception::log($this);

        if (Kohana::$environment >= Kohana::DEVELOPMENT)
        {
            // Show the normal Kohana error page.
            return parent::get_response();
        }
        else
        {
            // Generate a nicer looking "Oops" page.
            $view = View::factory('errors/default');

            $response = Response::factory()
                ->status($this->getCode())
                ->body($view->render());

            return $response;
        }
    }
}