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Session Proxy Examples

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Session Proxy Examples

The session proxy mechanism has a variety of uses and this article demonstrates two common uses. Rather than using the regular session handler, you can create a custom save handler just by defining a class that extends the SessionHandlerProxy class.

Then, define a new service related to the custom session handler:

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    # app/config/services.yml
services:
    app.session_handler:
        class: AppBundle\Session\CustomSessionHandler
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    <!-- app/config/services.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
        http://symfony.com/schema/dic/services/services-1.0.xsd">

    <services>
        <service id="app.session_handler" class="AppBundle\Session\CustomSessionHandler" />
    </services>
</container>
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    // app/config/config.php
use AppBundle\Session\CustomSessionHandler;

$container->register('app.session_handler', CustomSessionHandler::class);

Finally, use the framework.session.handler_id configuration option to tell Symfony to use your own session handler instead of the default one:

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    # app/config/config.yml
framework:
    session:
        # ...
        handler_id: app.session_handler
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    <!-- app/config/config.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:framework="http://symfony.com/schema/dic/symfony"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
        http://symfony.com/schema/dic/services/services-1.0.xsd">

    <framework:config>
        <framework:session handler-id="app.session_handler" />
    </framework:config>
</container>
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    // app/config/config.php
$container->loadFromExtension('framework', array(
    // ...
    'session' => array(
        // ...
        'handler_id' => 'app.session_handler',
    ),
));

Keep reading the next sections to learn how to use the session handlers in practice to solve two common use cases: encrypt session information and define readonly guest sessions.

Encryption of Session Data

If you want to encrypt the session data, you can use the proxy to encrypt and decrypt the session as required. The following example uses the php-encryption library, but you can adapt it to any other library that you may be using:

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// src/AppBundle/Session/EncryptedSessionProxy.php
namespace AppBundle\Session;

use Defuse\Crypto\Crypto;
use Defuse\Crypto\Key;
use Symfony\Component\HttpFoundation\Session\Storage\Proxy\SessionHandlerProxy;

class EncryptedSessionProxy extends SessionHandlerProxy
{
    private $key;

    public function __construct(\SessionHandlerInterface $handler, Key $key)
    {
        $this->key = $key;

        parent::__construct($handler);
    }

    public function read($id)
    {
        $data = parent::read($id);

        return Crypto::decrypt($data, $this->key);
    }

    public function write($id, $data)
    {
        $data = Crypto::encrypt($data, $this->key);

        return parent::write($id, $data);
    }
}

Readonly Guest Sessions

There are some applications where a session is required for guest users, but where there is no particular need to persist the session. In this case you can intercept the session before it is written:

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// src/AppBundle/Session/ReadOnlySessionProxy.php
namespace AppBundle\Session;

use AppBundle\Entity\User;
use Symfony\Component\HttpFoundation\Session\Storage\Proxy\SessionHandlerProxy;

class ReadOnlySessionProxy extends SessionHandlerProxy
{
    private $user;

    public function __construct(\SessionHandlerInterface $handler, User $user)
    {
        $this->user = $user;

        parent::__construct($handler);
    }

    public function write($id, $data)
    {
        if ($this->user->isGuest()) {
            return;
        }

        return parent::write($id, $data);
    }
}

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.