Sessions

CakePHP provides a wrapper and suite of utility features on top of PHP’s native session extension. Sessions allow you to identify unique users across requests and store persistent data for specific users. Unlike Cookies, session data is not available on the client side. Usage of $_SESSION is generally avoided in CakePHP, and instead usage of the Session classes is preferred.

Session Configuration

Session configuration is generally defined in /config/app.php. The available options are:

  • Session.timeout - The number of minutes before CakePHP’s session handler expires the session.
  • Session.defaults - Allows you to use the built-in default session configurations as a base for your session configuration. See below for the built-in defaults.
  • Session.handler - Allows you to define a custom session handler. The core database and cache session handlers use this. See below for additional information on Session handlers.
  • Session.ini - Allows you to set additional session ini settings for your config. This combined with Session.handler replace the custom session handling features of previous versions
  • Session.cookie - The name of the cookie to use. Defaults to ‘CAKEPHP’.
  • Session.cookiePath - The url path for which session cookie is set. Maps to the session.cookie_path php.ini config. Defaults to base path of app.

CakePHP’s defaults session.cookie_secure to true, when your application is on an SSL protocol. If your application serves from both SSL and non-SSL protocols, then you might have problems with sessions being lost. If you need access to the session on both SSL and non-SSL domains you will want to disable this:

Configure::write('Session', [
    'defaults' => 'php',
    'ini' => [
        'session.cookie_secure' => false
    ]
]);

The session cookie path defaults to app’s base path. To change this you can use the session.cookie_path ini value. For example if you want your session to persist across all subdomains you can do:

Configure::write('Session', [
    'defaults' => 'php',
    'ini' => [
        'session.cookie_path' => '/',
        'session.cookie_domain' => '.yourdomain.com'
    ]
]);

By default PHP sets the session cookie to expire as soon as the browser is closed, regardless of the configured Session.timeout value. The cookie timeout is controlled by the session.cookie_lifetime ini value and can be configured using:

Configure::write('Session', [
    'defaults' => 'php',
    'ini' => [
        // Invalidate the cookie after 30 minutes without visiting
        // any page on the site.
        'session.cookie_lifetime' => 1800
    ]
]);

The difference between Session.timeout and the session.cookie_lifetime value is that the latter relies on the client telling the truth about the cookie. If you require stricter timeout checking, without relying on what the client reports, you should use Session.timeout.

Please note that Session.timeout corresponds to the total time of inactivity for a user (i.e. the time without visiting any page where the session is used), and does not limit the total amount of minutes a user can stay on the site.

Built-in Session Handlers & Configuration

CakePHP comes with several built-in session configurations. You can either use these as the basis for your session configuration, or you can create a fully custom solution. To use defaults, simply set the ‘defaults’ key to the name of the default you want to use. You can then override any sub setting by declaring it in your Session config:

Configure::write('Session', [
    'defaults' => 'php'
]);

The above will use the built-in ‘php’ session configuration. You could augment part or all of it by doing the following:

Configure::write('Session', [
    'defaults' => 'php',
    'cookie' => 'my_app',
    'timeout' => 4320 // 3 days
]);

The above overrides the timeout and cookie name for the ‘php’ session configuration. The built-in configurations are:

  • php - Saves sessions with the standard settings in your php.ini file.
  • cake - Saves sessions as files inside tmp/sessions. This is a good option when on hosts that don’t allow you to write outside your own home dir.
  • database - Use the built-in database sessions. See below for more information.
  • cache - Use the built-in cache sessions. See below for more information.

Session Handlers

Session handlers can also be defined in the session config array. By defining the ‘handler.engine’ config key, you can name the class name, or provide a handler instance. The class/object must implement the native PHP SessionHandlerInterface. Implementing this interface will allow Session to automatically map the methods for the handler. Both the core Cache and Database session handlers use this method for saving sessions. Additional settings for the handler should be placed inside the handler array. You can then read those values out from inside your handler:

'Session' => [
    'handler' => [
        'engine' => 'Database',
        'model' => 'CustomSessions'
    ]
]

The above shows how you could setup the Database session handler with an application model. When using class names as your handler.engine, CakePHP will expect to find your class in the Network\Session namespace. For example, if you had an AppSessionHandler class, the file should be src/Network/Session/AppSessionHandler.php, and the class name should be App\Network\Session\AppSessionHandler. You can also use session handlers from inside plugins. By setting the engine to MyPlugin.PluginSessionHandler.

Database Sessions

If you need to use a database to store your session data, configure as follows:

'Session' => [
    'defaults' => 'database'
]

This configuration will require a database table to be added with at least these fields:

CREATE TABLE `sessions` (
  `id` varchar(255) NOT NULL DEFAULT '',
  `data` BLOB, -- or BYTEA for PostgreSQL
  `expires` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
);

You can find a copy of the schema for the sessions table in the application skeleton.

You can also use your own Table class to handle the saving of the sessions:

'Session' => [
    'defaults' => 'database',
    'handler' => [
        'engine' => 'Database',
        'model' => 'CustomSessions'
    ]
]

The above will tell Session to use the built-in ‘database’ defaults, and specify that a Table called CustomSessions will be the delegate for saving session information to the database.

Cache Sessions

The Cache class can be used to store sessions as well. This allows you to store sessions in a cache like APC, Memcached, or XCache. There are some caveats to using cache sessions, in that if you exhaust the cache space, sessions will start to expire as records are evicted.

To use Cache based sessions you can configure you Session config like:

Configure::write('Session', [
    'defaults' => 'cache',
    'handler' => [
        'config' => 'session'
    ]
]);

This will configure Session to use the CacheSession class as the delegate for saving the sessions. You can use the ‘config’ key which cache configuration to use. The default cache configuration is 'default'.

Setting ini directives

The built-in defaults attempt to provide a common base for session configuration. You may need to tweak specific ini flags as well. CakePHP exposes the ability to customize the ini settings for both default configurations, as well as custom ones. The ini key in the session settings, allows you to specify individual configuration values. For example you can use it to control settings like session.gc_divisor:

Configure::write('Session', [
    'defaults' => 'php',
    'ini' => [
        'session.cookie_name' => 'MyCookie',
        'session.cookie_lifetime' => 1800, // Valid for 30 minutes
        'session.gc_divisor' => 1000,
        'session.cookie_httponly' => true
    ]
]);

Creating a Custom Session Handler

Creating a custom session handler is straightforward in CakePHP. In this example we’ll create a session handler that stores sessions both in the Cache (APC) and the database. This gives us the best of fast IO of APC, without having to worry about sessions evaporating when the cache fills up.

First we’ll need to create our custom class and put it in src/Network/Session/ComboSession.php. The class should look something like:

namespace App\Network\Session;

use Cake\Cache\Cache;
use Cake\Core\Configure;
use Cake\Network\Session\DatabaseSession;

class ComboSession extends DatabaseSession
{
    public $cacheKey;

    public function __construct()
    {
        $this->cacheKey = Configure::read('Session.handler.cache');
        parent::__construct();
    }

    // Read data from the session.
    public function read($id)
    {
        $result = Cache::read($id, $this->cacheKey);
        if ($result) {
            return $result;
        }
        return parent::read($id);
    }

    // Write data into the session.
    public function write($id, $data)
    {
        Cache::write($id, $data, $this->cacheKey);
        return parent::write($id, $data);
    }

    // Destroy a session.
    public function destroy($id)
    {
        Cache::delete($id, $this->cacheKey);
        return parent::destroy($id);
    }

    // Removes expired sessions.
    public function gc($expires = null)
    {
        return Cache::gc($this->cacheKey) && parent::gc($expires);
    }
}

Our class extends the built-in DatabaseSession so we don’t have to duplicate all of its logic and behavior. We wrap each operation with a Cake\Cache\Cache operation. This lets us fetch sessions from the fast cache, and not have to worry about what happens when we fill the cache. Using this session handler is also easy. In your app.php make the session block look like the following:

'Session' => [
    'defaults' => 'database',
    'handler' => [
        'engine' => 'ComboSession',
        'model' => 'Session',
        'cache' => 'apc'
    ]
],
// Make sure to add a apc cache config
'Cache' => [
    'apc' => ['engine' => 'Apc']
]

Now our application will start using our custom session handler for reading and writing session data.

class Session

Accessing the Session Object

You can access the session data any place you have access to a request object. This means the session is accessible from:

  • Controllers
  • Views
  • Helpers
  • Cells
  • Components

In addition to the basic session object, you can also use the Cake\View\Helper\SessionHelper to interact with the session in your views. A basic example of session usage would be:

$name = $this->request->session()->read('User.name');

// If you are accessing the session multiple times,
// you will probably want a local variable.
$session = $this->request->session();
$name = $session->read('User.name');

Reading & Writing Session Data

Session::read($key)

You can read values from the session using Hash::extract() compatible syntax:

$session->read('Config.language');
Session::write($key, $value)

$key should be the dot separated path you wish to write $value to:

$session->write('Config.language', 'en');

You may also specify one or multiple hashes like so:

$session->write([
  'Config.theme' => 'blue',
  'Config.language' => 'en',
]);
Session::delete($key)

When you need to delete data from the session, you can use delete():

$session->delete('Some.value');
static Session::consume($key)

When you need to read and delete data from the session, you can use consume():

$session->consume('Some.value');
Session::check($key)

If you want to see if data exists in the session, you can use check():

if ($session->check('Config.language')) {
    // Config.language exists and is not null.
}

Destroying the Session

Session::destroy()

Destroying the session is useful when users log out. To destroy a session, use the destroy() method:

$session->destroy();

Destroying a session will remove all serverside data in the session, but will not remove the session cookie.

Rotating Session Identifiers

Session::renew()

While AuthComponent automatically renews the session id when users login and logout, you may need to rotate the session id’s manually. To do this use the renew() method:

$session->renew();

Flash Messages

Flash messages are small messages displayed to end users once. They are often used to present error messages, or confirm that actions took place successfully.

To set and display flash messages you should use Flash and Flash