Session Handling

Flow has excellent support for working with sessions.

This chapter will explain:

  • … how to store specific data in a session
  • … how to store objects in the session
  • … how to delete sessions

Scope Session

Flow does not only support the prototype and singleton object scopes, but also the object scope session. Objects marked like this basically behave like singleton objects which are automatically serialized into the user’s session.

As an example, when building a shopping basket, the class could look as follows:

/**
 * @Flow\Scope("session")
 */
class ShoppingBasket {

        /**
         * @var array
         */
        protected $items = array();

        /**
         * @param string $item
         * @return void
         * @Flow\Session(autoStart = TRUE)
         */
        public function addItem($item) {
                $this->items[] = $item;
        }

        /**
         * @return array
         */
        public function getItems() {
                return $this->items;
        }
}

In the above example

  • the object scope is set to session, so it behaves like a user-bound cross-request singleton. This ShoppingBasket can now be injected where it is needed using Dependency Injection.
  • We only want to start a session when the first element is added to the shopping basket. For this the addItem() method needs to be annotated with @Flow\Session(autoStart = TRUE).

When a user browses the website, the following then happens:

  • First, the user’s shopping basket is empty, and getItems() returns an empty array. No session exists yet. For each page being requested, the ShoppingBasket is newly initialized.
  • As soon as the user adds something to the shopping basket, addItem() is called. Because this is annotated with @Flow\Session(autoStart = TRUE), a new PHP session is started, and the ShoppingBasket is placed into the session.
  • As the user continues to browse the website, the ShoppingBasket is being fetched from the user’s session (which exists now). Thus, getItems() returns the items from the session.

Why is @Flow\Session(autoStart = TRUE) necessary?

If Flow did not have this annotation, there would be no way for it to determine when a session must be started. Thus, every user browsing the website would always need a session as soon as an object of scope session is accessed. This would happens if the session-scoped object is still in its initial state.

To be able to use proxies such as Varnish, Flow defers the creation of a session to a point in time when it is really needed – and the developer needs to tell the framework when that point is reached using the above annotation.

The Flow session scope handles persistent objects and dependency injection correctly:

  • Objects which are injected via Dependency Injection are removed before serialization and re-injected on deserialization.
  • Persistent objects which are unchanged are just stored as a reference and fetched from persistence again on deserialization.
  • Persistent objects which are modified are fully stored in the session.

Low-level session handling

It is possible to inject the Neos\Flow\Session\SessionInterface and interact with the session on a low level, by using start(), getData() and putData().

That should rarely be needed, though. Instead of manually serializing objects object into the session, the session scope should be used whenever possible.

Session Backends

The session implementation of Flow is written in pure PHP and uses the caching framework as its storage. This allows for storing session data in a variety of backends, including PDO databases, APC and Redis.

The preferred storage backend for the built-in session is defined through a custom Caches.yaml file, placed in a package or the global configuration directory:

Flow_Session_Storage:
  backend: Neos\Cache\Backend\RedisBackend

The built-in session implementation provides a few more configuration options, related to the session cookie and the automatic garbage collection. Please refer to the Settings.yaml file of the Flow package for a list of all possible options and their respective documentation.

Session Storage

Note

Since Flow 5.2 Sessions are no longer destroyed by default when caches are flushed. This is due to the session caches being marked as “persistent”. This previously lead to all sessions being destroyed on each deployment, which was undesireable.

If you deploy changes that change the structure of data that is stored in the session or the class of an @Flowscope(“session”) object, you need to manually destroy sessions to avoid deserialization errors. You can do this by running ./flow flow:session:destroyAll or manually deleting the folder where the sessions are stored.

Also, sessions are shared among the application contexts, e.g. Development and Production, so if your use case requires to have sessions separated for different contexts, you need to configure the cacheDirectory backend option for the Flow_Session_Storage and Flow_Session_MetaData caches for each individual context. Please refer to the Cache Framework section of this guide for further information.