25.3. Advanced Usage
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## 25.3. Advanced Usage

While the basic usage examples are a perfectly acceptable way to utilize Zend Framework sessions, there are some best practices to consider. Consider the `Zend_Auth` example that transparently uses Zend_Session_Namespace by default to persist authentication tokens. This example shows one approach to quickly and easily integrate Zend_Session_Namespace and Zend_Auth.

### 25.3.1. Starting a Session

If you want all requests to have a session and use Zend Framework sessions, then start the session in the bootstrap file:

Beispiel 25.6. Starting the Global Session

    <?php
    ...
    require_once 'Zend/Session.php';
    Zend_Session::start();
    ...
    ?>

By starting the session in the bootstrap file, you avoid the possibility that your session might be started after headers have been sent to the browser, which results in an exception, and possibly a broken page for website viewers. Various advanced features require `Zend_Session::start()` first. (More on advanced features later.)

There are four ways to start a session, when using Zend_Session. Two are wrong.

- 1. Wrong: Do not set PHP's session.auto_start ini setting in either php.ini or .htaccess (http://www.php.net/manual/en/ref.session.php#ini.session.auto-start). If you do not have the ability to disable this setting in php.ini, you are using mod_php (or equivalent), and the setting is already enabled in php.ini, then add `php_value session.auto_start 0` to your .htaccess file (usually in your HTML document root directory).

- 2. Wrong: Do not use PHP's `session_start()` function directly If you use `session_start()` directly, and then start using Zend_Session_Namespace, an exception will be thrown by `Zend_Session::start()` ("session has already been started"). If you call `session_start()`, after using Zend_Session_Namespace or starting `Zend_Session::start()` explicitly, an error of level E_NOTICE will be generated, and the call will be ignored.

- 3. Correct: Use `Zend_Session::start()`. If you want all requests to have and use sessions, then place this function call early and unconditionally in your ZF bootstrap code. Sessions have some overhead. If some requests need sessions, but other requests will not need to use sessions, then:

  - Unconditionally, set the `strict` option to true (see `Zend_Session::setOptions()` ) in your userland bootstrap.

  - Call `Zend_Session::start()`, only for requests that need to use sessions, before the first call to `new Zend_Session_Namespace()`.

  - Use `new Zend_Session_Namespace()` normally, where needed, but make sure `Zend_Session::start()` has been called previously.

  The `strict` option prevents `new Zend_Session_Namespace()` from automatically starting the session using `Zend_Session::start()`. Thus, this option helps developers of userland ZF applications enforce a design decision to avoid using sessions for certain requests, since an error will be thrown when using this option and instantiating Zend_Session_Namespace, before an explicit call to `Zend_Session::start()`. Do not use this option in ZF core library code, because only userland developers should make this design choice. Similarly, all "library" developers should carefully consider the impact of using `Zend_Session::setOptions()` on users of their library code, since these options have global side-effects (as do the underlying options for ext/session).

- 4. Correct: Just use `new Zend_Session_Namespace()` whenever needed, and the session will be automatically started within Zend_Session. This offers extremely simple usage that works well in most situations. However, you then become responsible for ensuring that the first `new Zend_Session_Namespace()` happens before any output (i.e. HTTP headers ) has been sent by PHP to the client, if you are using the default, cookie-based sessions (strongly recommended). Using output buffering often is sufficient to prevent this issue and may help improve performance. For example, in `php.ini`, "`output_buffering = 65535`" enables output buffering with a 64K buffer.

### 25.3.2. Locking Session Namespaces

Session namespaces can be locked, to prevent further alterations to the data in that namespace. Use `Zend_Session_Namespace's lock()` to make a specific namespace read-only, `unLock()` to make a read-only namespace read-write, and `isLocked()` to test if a namespace has been previously locked. Locks are transient and do not persist from one request to the next. Locking the namespace has no effect on setter methods of objects stored in the namespace, but does prevent the use of the namespace's setter method to remove or replace objects stored directly in the namespace. Similarly, locking Zend_Session_Namespace namespaces does not prevent the use of symbol table aliases to the same data (see PHP references ).

Beispiel 25.7. Locking Session Namespaces

    <?php
        // assuming:
        $userProfileNamespace = new Zend_Session_Namespace('userProfileNamespace');

        // marking session as read only locked
        $userProfileNamespace->lock();

        // unlocking read-only lock
        if ($userProfileNamespace->isLocked()) {
            $userProfileNamespace->unLock();
        }
    ?>

There are numerous ideas for how to manage models in MVC paradigms for the Web, including creating presentation models for use by views. Sometimes existing data, whether part of your domain model or not, is adequate for the task. To discourage views from applying any processing logic to alter such data, consider locking session namespaces before permitting views to access this subset of your "presentation" model.

Beispiel 25.8. Locking Sessions in Views

    <?php
    class FooModule_View extends Zend_View
    {
        public function show($name)
        {
            if (!isset($this->mySessionNamespace)) {
                $this->mySessionNamespace = Zend::registry('FooModule');
            }

            if ($this->mySessionNamespace->isLocked()) {
                return parent::render($name);
            }

            $this->mySessionNamespace->lock();
            $return = parent::render($name);
            $this->mySessionNamespace->unLock();

            return $return;
        }
    }
    ?>

### 25.3.3. Session Encapsulation and Controllers

Namespaces can also be used to separate session access by controllers to protect variables from contamination. For example, the 'Zend_Auth' controller might keep its session state data separate from all other controllers.

Beispiel 25.9. Namespaced Sessions for Controllers with Automatic Expiration

    <?php
    require_once 'Zend/Session.php';
    // question view controller
    $testSpace = new Zend_Session_Namespace('testSpace');
    $testSpace->setExpirationSeconds(300, "accept_answer"); // expire only this variable
    $testSpace->accept_answer = true;

    --

    // answer processing controller
    $testSpace = new Zend_Session('testSpace');

    if ($testSpace->accept_answer === true) {
        // within time
    }
    else {
        // not within time
    }
    ?>

### 25.3.4. Limiting Instances of Zend_Session_Namespace to One Per Namespace

We recommend using session locking (see above) instead of the feature below, which places extra management burden on the developer to pass any Zend_Session_Namespace instances into whatever functions and objects need access to each namespace.

When constructing the first instance of Zend_Session_Namespace attached to a specific namespace, you can also instruct Zend_Session_Namespace to not make any more instances for that namespace. Thus, any future attempts to construct a Zend_Session_Namespace instance having the same namespace will throw an error. Such behavior is optional, and not the default behavior, but remains available to those who prefer to pass around a single instance object for each namespace. This increases protection from changes by components that should not modify a particular session namespace, because they won't have easy access. However, limiting a namespace to a single instance may lead to more code or more complex code, as it removes access to the convient `$aNamespace = new Zend_Session_Namespace('aNamespace');`, after the first intance has been created, as follows in the example below:

Beispiel 25.10. Limiting to Single Instances

    <?php
        require_once 'Zend/Session.php';
        $authSpaceAccessor1 = new Zend_Session_Namespace('Zend_Auth');
        $authSpaceAccessor2 = new Zend_Session_Namespace('Zend_Auth', Zend_Session_Namespace::SINGLE_INSTANCE);
        $authSpaceAccessor1->foo = 'bar';
        assert($authSpaceAccessor2->foo, 'bar'); // passes
        doSomething($options, $authSpaceAccessor2); // pass the accessor to wherever it is needed
        .
        .
        .
        $aNamespaceObject = new Zend_Session_Namespace('Zend_Auth'); // this will throw an error
    ?>

The second parameter in the constructor above will tell Zend_Session_Namespace that any future Zend_Session's that are instantiated with the 'Zend_Auth' namespace are not allowed, and will thus cause an exception. Since `new Zend_Session_Namespace('Zend_Auth')` will not be allowed after the code above has been executed, the developer becomes responsible for storing the instance object (`$authSpaceAccessor2` in the example above) somewhere, if access to this session namespace is needed at a later time during the same request. For example, a developer may store the instance in a static variable, or pass it to other methods that might need access to this session namespace. Session locking (see above) provides a more convenient, and less burdensome approach to limiting access to namespaces.

### 25.3.5. Working with Arrays in Namespaces

Modifying an array inside a namespace does not work. The simplest solution is to store arrays after all desired values have been set. ZF-800 documents a known issue affecting many PHP applications using magic methods and arrays.

Beispiel 25.11. Known problem with arrays

    <?php
        $sessionNamespace = new Zend_Session_Namespace('Foo');
        $sessionNamespace->array = array();
        $sessionNamespace->array['testKey'] = 1; // does not work before PHP 5.2.1
    ?>

If you need to modify the array after assigning it to a session namespace key, fetch the array, then

Beispiel 25.12. Workaround: fetch, modify, save

    <?php
        $sessionNamespace = new Zend_Session_Namespace('Foo');
        $sessionNamespace->array = array('tree' => 'apple');
        $tmp = $sessionNamespace->array;
        $tmp['fruit'] = 'peach';
        $sessionNamespace->array = $tmp;
    ?>

Alternatively, store an array containing a reference to the desired array, and then access it indirectly.

Beispiel 25.13. Workaround: store array containing reference

    <?php
        $myNamespace = new Zend_Session_Namespace('mySpace');

        // works, even for broken versions of PHP
        $a = array(1,2,3);
        $myNamespace->someArray = array( & $a ) ;
        $a['foo'] = 'bar';
    ?>

### 25.3.6. Using Sessions with Authentication

If you allow `Zend_Auth` to persist authentication tokens using Zend Framework sessions. In order to access the authentication token on subsequent requests, you would need to:

Beispiel 25.14. Workaround: accessing authentication tokens in sessions

    <?php
        // chicken-and-egg... you must know which token class before looking :(
        require_once 'Zend/Auth/Digest/Token.php';
        require_once 'Zend/Session.php';
        Zend_Session::start();
        require_once 'Zend/Auth/Digest/Adapter.php';
        require_once 'Zend/Auth.php';
        $auth = new Zend_Auth(new Zend_Auth_Digest_Adapter('someDigestFilename'));
        $token = $auth->getToken();
        echo "Valid: ",
        (empty($token->isValid()) ? 'No' : 'Yes'), "\n"';
        echo "Identity: ",
            (empty($token->getIdentity()) ? 'unknown' : $token->getIdentity()), "\n"';
        echo "Messages: ",
            (empty($token->getMessages()) ? 'none' : $token->getMessages()), "\n"';
    ?>

If you tell `Zend_Auth` to not persist authentication tokens in sessions, and then manually store the authorization id to the session, then just use well-known locations in a session namespace. Also, this avoids persisting authentication error messages in the session. (Note: Some community members are working on a "flash message" system for Zend sessions.) Often, applications have specific needs about where to store credentials used (if any) and "authorization" identity. Applications often map authentication identities (e.g. usernames) to authorization identities (e.g. a uniquely assigned integer) during authentication.

Beispiel 25.15. Workaround: simpler access for authorization ids

    <?php
        require 'Zend/Session.php';
        Zend_Session::start();
        $namespace = Zend_Session_Namespace('Zend_Auth');

        echo "Valid: ", (empty($namespace->authorizationId) ? 'No' : 'Yes'), "\n"';
        echo "Authorization / user Id: ",
            (empty($namespace->authorizationId) ? 'none' : $namespace->authorizationId), "\n"';
        echo "Authentication attempts: ",
            (empty($namespace->attempts) ? '0' : $namespace->attempts), "\n"';
        echo "Authenticated on: ",
            (empty($namespace->date) ? 'No' : date(DATE_ATOM, $namespace->date), "\n"';
    ?>

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