Using Symfony Dependency Injection with Zend_Application

As a follow-up to my recent post on Dependency Injection containers and Zend_Application I was eager to find out if its possible to integrate the new Symfony Dependency Injection Container into the Zend Framework. To my surprise it’s possible without having to make any changes to one of the two components. An example use-case would look like:

$container = new sfServiceContainerBuilder();

$loader = new sfServiceContainerLoaderFileXml($container);
$loader->load(APPLICATION_PATH.'/config/objects.xml');

$application = new Zend_Application(
    APPLICATION_ENV,
    APPLICATION_PATH . '/config/application.xml'
);
$application->getBootstrap()->setContainer($container);
$application->bootstrap()
            ->run();

Resources instantiated by Zend_Application are then injected into the container by the name of the resource and are given the resource instance. Any object from the Symfony container can then use these dependencies in their object setup. The only drawback of the integration is the fact that the Symfony Container is case-sensitive in regards to the service names but Zend_Application lower-cases all service before injecting them into the container. The following code is a restatement of my previous example of a MyModel class which requires a Zend_Db and Zend_Cache constructor argument.

$container->register('myModel', 'MyModel')
          ->addArgument(new sfServiceReference('db'))
          ->addArgument(new sfServiceReference('cache'));

Access to a MyModel instance with its dependencies is then granted through the call $container->myModel throughout the application. Make sure to call this after running Zend_Application::bootstrap, so that the Resource dependencies are injected first.