If no namespace is specified when instantiating Zend_Session_Namespace, all data will be transparently stored in a namespace called "Default". Zend_Session is not intended to work directly on the contents of session namespace containers. Instead, we use Zend_Session_Namespace. The example below demonstrates use of this default namespace, showing how to count the number of client requests during a session:

$defaultNamespace = new Zend_Session_Namespace('Default');

if (isset($defaultNamespace->numberOfPageRequests)) {
    // this will increment for each page load.
    $defaultNamespace->numberOfPageRequests++;
} else {
    $defaultNamespace->numberOfPageRequests = 1; // first time
}

echo "Page requests this session: ",
    $defaultNamespace->numberOfPageRequests;

When multiple modules use instances of Zend_Session_Namespace having different namespaces, each module obtains data encapsulation for its session data. The Zend_Session_Namespace constructor can be passed an optional $namespace argument, which allows developers to partition session data into separate namespaces. Namespacing provides an effective and popular way to secure session state data against changes due to accidental naming collisions.

Namespace names are restricted to character sequences represented as non-empty PHP strings that do not begin with an underscore ("_") character. Only core components included in Zend Framework should use namespace names starting with "Zend".

// in the Zend_Auth component
$authNamespace = new Zend_Session_Namespace('Zend_Auth');
$authNamespace->user = "myusername";

// in a web services component
$webServiceNamespace = new Zend_Session_Namespace('Some_Web_Service');
$webServiceNamespace->user = "mywebusername";

The example above achieves the same effect as the code below, except that the session objects above preserve encapsulation of session data within their respective namespaces.

$_SESSION['Zend_Auth']['user'] = "myusername";
$_SESSION['Some_Web_Service']['user'] = "mywebusername";

Zend_Session_Namespace provides the full IteratorAggregate interface, including support for the foreach statement:

$aNamespace =
    new Zend_Session_Namespace('some_namespace_with_data_present');

foreach ($aNamespace as $index => $value) {
    echo "aNamespace->$index = '$value';\n";
}

Zend_Session_Namespace implements the __get(), __set(), __isset(), and __unset() magic methods, which should not be invoked directly, except from within a subclass. Instead, the normal operators automatically invoke these methods, such as in the following example:

$namespace = new Zend_Session_Namespace(); // default namespace

$namespace->foo = 100;

echo "\$namespace->foo = $namespace->foo\n";

if (!isset($namespace->bar)) {
    echo "\$namespace->bar not set\n";
}

unset($namespace->foo);