Redirecting to a new URL

        // anywhere, but preferrably inside a controller
        HTTP::redirect('/somehwere-else/');

Check if the user has requested the page through ajax

        // inside a controller
        if ($this->request->is_ajax()) { // do some stuff }

        // anywhere else
        if (Request::initial()->is_ajax()) { // do some stuff }

Make the content download instead of sending to the browser

        $data = 'some data generated or fetched from somewhere';
        $this->response->body($data);
        $this->response->send_file(TRUE, 'data.txt');  // data.txt will be downloaded by browser, containing contents of the $data variable

        $filepath = DOCROOT . 'downloads/myfiles/data.zip';  // just an example
        $this->response->send_file($filepath, 'data.zip');   // data.zip will be downloaded by browser (you can skip the second parameter also)

        // delete the file after sending to the browser automatically
        $this->response->send_file($filepath, 'something.zip', array('delete' => TRUE));

Ideally you will almost always use download functionality inside your controller. Will be really strange to be using it elsewhere!.

Getting configuration variables

        // get the name of default database our application uses
        $db_name = Kohana::$config->load('database.default.connection.database');

        // get the default database character set being used
        $db_charset = Kohana::$config->load('database.default.charset');

        // get the whole database configuration
        $db_info = Kohana::$config->load('database');

Logging errors and messages

        Kohana::$log->add(Log::ERROR, 'something wrong happened');

        Kohana::$log->add(Log::INFO, 'user registration completed');

        Kohana::$log->add(Log::INFO, 'user :user logged in at :time', array(
            ':user' => $user->login_id,
            ':time' => date("Y-m-d H:i:s")
        ));

        Kohana::$log->add(Log::DEBUG, 'debug information for some reason');

You can control whether the log statements in your code actually go into the log or get ignored. See Kohana documentation of Log class to find out how to do that.

Using Session variables

        $session = Session::instance();  // session type depends on the config you set (e.g. native PHP sessions, stored inside db etc)

        $session->set('user_id', $user->id);

        $user_id = $session->get('user_id');

        $session->delete('user_id');

Exceptions

        // throw a 404 exception for a missing downloadable file
        if (!file_exists($download_file)) {
            throw new Http_Exception_404('Download file invalid: :file',
                array(':file' => $download_file)
            );
            // another way to do the same
            throw Http_Exception::factory(404, 'Download file invalid: :file',
                array(':file' => $download_file)
            );
        }

In the next section, we will be creating additional routes to see the power of Kohana 3 routes and their use in a real application.