Cookies

Kohana provides classes that make it easy to work with both cookies and sessions. At a high level both sessions and cookies provide the same functionality. They allow the developer to store temporary or persistent information about a specific client for later retrieval, usually to make something persistent between requests.

Cookies should be used for storing non-private data that is persistent for a long period of time. For example storing a user preference or a language setting. Use the Cookie class for getting and setting cookies.

Kohana uses "signed" cookies. Every cookie that is stored is combined with a secure hash to prevent modification of the cookie. If a cookie is modified outside of Kohana the hash will be incorrect and the cookie will be deleted. This hash is generated using Cookie::salt(), which uses the Cookie::$salt property. You must define this setting in your bootstrap.php:

Cookie::$salt = 'foobar';

Or define an extended cookie class in your application:

class Cookie extends Kohana_Cookie
{
    public static $salt = 'foobar';
}

You should set the salt to a secure value. The example above is only for demonstrative purposes.

Nothing stops you from using $_COOKIE like normal, but you can not mix using the Cookie class and the regular $_COOKIE global, because the hash that Kohana uses to sign cookies will not be present, and Kohana will delete the cookie.

Storing, Retrieving, and Deleting Data

Cookie and Session provide a very similar API for storing data. The main difference between them is that sessions are accessed using an object, and cookies are accessed using a static class.

Storing Data

Storing session or cookie data is done using the Cookie::set method:

// Set cookie data
Cookie::set($key, $value);

// Store a user id
Cookie::set('user_id', 10);

Retrieving Data

Getting session or cookie data is done using the Cookie::get method:

// Get cookie data
$data = Cookie::get($key, $default_value);

// Get the user id
$user = Cookie::get('user_id');

Deleting Data

Deleting session or cookie data is done using the Cookie::delete method:

// Delete cookie data
Cookie::delete($key);

// Delete the user id
Cookie::delete('user_id');

Cookie Settings

All of the cookie settings are changed using static properties. You can either change these settings in bootstrap.php or by using transparent extension. Always check these settings before making your application live, as many of them will have a direct affect on the security of your application.

The most important setting is Cookie::$salt, which is used for secure signing. This value should be changed and kept secret:

Cookie::$salt = 'your secret is safe with me';

Changing this value will render all cookies that have been set before invalid.

By default, cookies are stored until the browser is closed. To use a specific lifetime, change the Cookie::$expiration setting:

// Set cookies to expire after 1 week
Cookie::$expiration = 604800;

// Alternative to using raw integers, for better clarity
Cookie::$expiration = Date::WEEK;

The path that the cookie can be accessed from can be restricted using the Cookie::$path setting.

// Allow cookies only when going to /public/*
Cookie::$path = '/public/';

The domain that the cookie can be accessed from can also be restricted, using the Cookie::$domain setting.

// Allow cookies only on the domain www.example.com
Cookie::$domain = 'www.example.com';

If you want to make the cookie accessible on all subdomains, use a dot at the beginning of the domain.

// Allow cookies to be accessed on example.com and *.example.com
Cookie::$domain = '.example.com';

To only allow the cookie to be accessed over a secure (HTTPS) connection, use the Cookie::$secure setting.

// Allow cookies to be accessed only on a secure connection
Cookie::$secure = TRUE;

// Allow cookies to be accessed on any connection
Cookie::$secure = FALSE;

To prevent cookies from being accessed using Javascript, you can change the Cookie::$httponly setting.

// Make cookies inaccessible to Javascript
Cookie::$httponly = TRUE;