The success of the web is deeply rooted in the protocol that drives the web: HTTP. HTTP over TCP is by its very nature stateless, which means that inherently the web is also stateless. While this very aspect is one of the dominating factors for why the web has become such a popular medium, it also causes an interesting problem for developers that want to use the web as an application platform.

The act of interacting with a web application is typically defined by the sum of all requests sent to a web server. Since there can be many consumers being served simultaneously, the application must decide which requests belong to which consumer. These requests are typically known as a "session".

In PHP, the session problem is solved by the session extension which utilizes some state tracking, typically cookies, and some form of local storage which is exposed via the $_SESSION superglobal. In Zend Framework, the component Zend_Session adds value to the PHP session extension making it easier to use and depend on inside object-oriented applications.

The Zend_Session component is both a session manager as well as an API for storing data into a session object for long-term persistence. The Zend_Session API is for managing the options and behavior of a session, like options, starting and stopping a session, whereas Zend_Session_Namespace is the actual object used to store data.

While its generally good practice to start a session inside a bootstrap process, this is generally not necessary as all sessions will be automatically started upon the first creation of a Zend_Session_Namespace object.

Zend_Application is capable of configuring Zend_Session for you as part of the Zend_Application_Resource system. To use this, assuming your project uses Zend_Application to bootstrap, you would add the following code to your application.ini file:

resources.session.save_path = APPLICATION_PATH "/../data/session"
resources.session.use_only_cookies = true
resources.session.remember_me_seconds = 864000

As you can see, the options passed in are the same options that you'd expect to find in the ext/session extension in PHP. Those options setup the path to the session files where data will be stored within the project. Since INI files can additionally use constants, the above will use the APPLICATION_PATH constant and relatively point to a data session directory.

Most Zend Framework components that use sessions need nothing more to use Zend_Session. At this point, you an either use a component that consumes Zend_Session, or start storing your own data inside a session with Zend_Session_Namespace.

Zend_Session_Namespace is a simple class that proxies data via an easy to use API into the Zend_Session managed $_SESSION superglobal. The reason it is called Zend_Session_Namespace is that it effectively namespaces the data inside $_SESSION, thus allowing multiple components and objects to safely store and retrieve data. In the following code, we'll explore how to build a simple session incrementing counter, starting at 1000 and resetting itself after 1999.

$mysession = new Zend_Session_Namespace('mysession');

if (!isset($mysession->counter)) {
    $mysession->counter = 1000;
} else {
    $mysession->counter++;
}

if ($mysession->counter > 1999) {
    unset($mysession->counter);
}

As you can see above, the session namespace object uses the magic __get, __set, __isset, and __unset to allow you to seamlessly and fluently interact with the session. The information stored in the above example is stored at $_SESSION['mysession']['counter'].

Additionally, if you wanted to use the DbTable save handler for Zend_Session, you'd add the following code to your application.ini:

resources.session.saveHandler.class = "Zend_Session_SaveHandler_DbTable"
resources.session.saveHandler.options.name = "session"
resources.session.saveHandler.options.primary.session_id = "session_id"
resources.session.saveHandler.options.primary.save_path = "save_path"
resources.session.saveHandler.options.primary.name = "name"
resources.session.saveHandler.options.primaryAssignment.sessionId = "sessionId"
resources.session.saveHandler.options.primaryAssignment.sessionSavePath = "sessionSavePath"
resources.session.saveHandler.options.primaryAssignment.sessionName = "sessionName"
resources.session.saveHandler.options.modifiedColumn = "modified"
resources.session.saveHandler.options.dataColumn = "session_data"
resources.session.saveHandler.options.lifetimeColumn = "lifetime"