The Module Manager

The module manager, Zend\ModuleManager\ModuleManager, is a very simple class which is responsible for iterating over an array of module names and triggering a sequence of events for each. Instantiation of module classes, initialization tasks, and configuration are all performed by attached event listeners.

Module Manager Events

Events triggered by Zend\ModuleManager\ModuleManager

loadModules

This event is primarily used internally to help encapsulate the work of loading modules in event listeners, and allow the loadModules.post event to be more user-friendly. Internal listeners will attach to this event with a negative priority instead of loadModules.post so that users can safely assume things like config merging have been done once loadModules.post is triggered, without having to worry about priorities at all.

loadModule.resolve

Triggered for each module that is to be loaded. The listener(s) to this event are responsible for taking a module name and resolving it to an instance of some class. The default module resolver shipped with ZF2 simply looks for the class {modulename}\Module, instantiating and returning it if it exists.

The name of the module may be retrieved by listeners using the getModuleName() method of the Event object; a listener should then take that name and resolve it to an object instance representing the given module. Multiple listeners can be attached to this event, and the module manager will trigger them in order of their priority until one returns an object. This allows you to attach additional listeners which have alternative methods of resolving modules from a given module name.

loadModule

Once a module resolver listener has resolved the module name to an object, the module manager then triggers this event, passing the newly created object to all listeners.

loadModules.post

This event is triggered by the module manager to allow any listeners to perform work after every module has finished loading. For example, the default configuration listener, Zend\ModuleManager\Listener\ConfigListener (covered later), attaches to this event to merge additional user-supplied configuration which is meant to override the default supplied configurations of installed modules.

Module Manager Listeners

By default, Zend Framework provides several useful module manager listeners.

Provided Module Manager Listeners

Zend\ModuleManager\Listener\DefaultListenerAggregate

To help simplify the most common use case of the module manager, ZF2 provides this default aggregate listener. In most cases, this will be the only listener you will need to attach to use the module manager, as it will take care of properly attaching the requisite listeners (those listed below) for the module system to function properly.

Zend\ModuleManager\Listener\AutoloaderListener

This listener checks each module to see if it has implemented Zend\ModuleManager\Feature\AutoloaderProviderInterface or simply defined the getAutoloaderConfig() method. If so, it calls the getAutoloaderConfig() method on the module class and passes the returned array to Zend\Loader\AutoloaderFactory.

Zend\ModuleManager\Listener\ModuleDependencyCheckerListener

This listener checks each module to verify if all the modules it depends on were loaded. When a module class implements Zend\ModuleManager\Feature\DependencyIndicatorInterface or simply has a defined getDependencyModules() method, the listener will call getDependencyModules(). Each of the values returned by the method is checked against the loaded modules list: if one of the values is not in that list, a Zend\ModuleManager\Exception\MissingDependencyModuleException is be thrown.

Zend\ModuleManager\Listener\ConfigListener

If a module class has a getConfig() method, or implements Zend\ModuleManager\Feature\ConfigProviderInterface, this listener will call it and merge the returned array (or Traversable object) into the main application configuration.

Zend\ModuleManager\Listener\InitTrigger

If a module class either implements Zend\ModuleManager\Feature\InitProviderInterface, or simply defines an init() method, this listener will call init() and pass the current instance of Zend\ModuleManager\ModuleManager as the sole parameter.

Like the OnBootstrapListener, the init() method is called for every module implementing this feature, on every page request and should only be used for performing lightweight tasks such as registering event listeners.

Zend\ModuleManager\Listener\LocatorRegistrationListener

If a module class implements Zend\ModuleManager\Feature\LocatorRegisteredInterface, this listener will inject the module class instance into the ServiceManager using the module class name as the service name. This allows you to later retrieve the module class from the ServiceManager.

Zend\ModuleManager\Listener\ModuleResolverListener

This is the default module resolver. It attaches to the “loadModule.resolve” event and simply returns an instance of {moduleName}\Module.

Zend\ModuleManager\Listener\OnBootstrapListener

If a module class implements Zend\ModuleManager\Feature\BootstrapListenerInterface, or simply defines an onBootstrap() method, this listener will register the onBootstrap() method with the Zend\Mvc\Application bootstrap event. This method will then be triggered during the bootstrap event (and passed an MvcEvent instance).

Like the InitTrigger, the onBootstrap() method is called for every module implementing this feature, on every page request, and should only be used for performing lightweight tasks such as registering event listeners.

Zend\ModuleManager\Listener\ServiceListener

If a module class implements Zend\ModuleManager\Feature\ServiceProviderInterface, or simply defines an getServiceConfig() method, this listener will call that method and aggregate the return values for use in configuring the ServiceManager.

The getServiceConfig() method may return either an array of configuration compatible with Zend\ServiceManager\Config, an instance of that class, or the string name of a class that extends it. Values are merged and aggregated on completion, and then merged with any configuration from the ConfigListener falling under the service_manager key. For more information, see the ServiceManager documentation.

Unlike the other listeners, this listener is not managed by the DefaultListenerAggregate; instead, it is created and instantiated within the Zend\Mvc\Service\ModuleManagerFactory, where it is injected with the current ServiceManager instance before being registered with the ModuleManager events.

Additionally, this listener manages a variety of plugin managers, including view helpers, controllers, and controller plugins. In each case, you may either specify configuration to define plugins, or provide configuration via a Module class. Configuration follows the same format as for the ServiceManager. The following table outlines the plugin managers that may be configured this way (including the ServiceManager), the configuration key to use, the ModuleManager feature interface to optionally implement (all interfaces specified live in the Zend\ModuleManager\Feature namespace) , and the module method to optionally define to provide configuration.

Plugin Manager	Config Key	Interface	Module Method
Zend\Mvc\Controller\ControllerManager	controllers	ControllerProviderInterface	getControllerConfig
Zend\Mvc\Controller\PluginManager	controller_plugins	ControllerPluginProviderInterface	getControllerPluginConfig
Zend\Filter\FilterPluginManager	filters	FilterProviderInterface	getFilterConfig
Zend\Form\FormElementManager	form_elements	FormElementProviderInterface	getFormElementConfig
Zend\Stdlib\Hydrator\HydratorPluginManager	hydrators	HydratorProviderInterface	getHydratorConfig
Zend\InputFilter\InputFilterPluginManager	input_filters	InputFilterProviderInterface	getInputFilterConfig
Zend\Mvc\Router\RoutePluginManager	route_manager	RouteProviderInterface	getRouteConfig
Zend\Serializer\AdapterPluginManager	serializers	SerializerProviderInterface	getSerializerConfig
Zend\ServiceManager\ServiceManager	service_manager	ServiceProviderInterface	getServiceConfig
Zend\Validator\ValidatorPluginManager	validators	ValidatorProviderInterface	getValidatorConfig
Zend\View\HelperPluginManager	view_helpers	ViewHelperProviderInterface	getViewHelperConfig

Configuration follows the examples in the ServiceManager configuration section. As a brief recap, the following configuration keys and values are allowed:

Config Key	Allowed values
services	service name/instance pairs (these should likely be defined only in Module classes)
invokables	service name/class name pairs of classes that may be invoked without constructor arguments
factories	service names pointing to factories. Factories may be any PHP callable, or a string class name of a class implementing Zend\ServiceManager\FactoryInterface, or of a class implementing the __invoke method (if a callable is used, it should be defined only in Module classes)
abstract_factories	array of either concrete instances of Zend\ServiceManager\AbstractFactoryInterface, or string class names of classes implementing that interface (if an instance is used, it should be defined only in Module classes)
initializers	array of PHP callables or string class names of classes implementing Zend\ServiceManager\InitializerInterface (if a callable is used, it should be defined only in Module classes)

When working with plugin managers, you will be passed the plugin manager instance to factories, abstract factories, and initializers. If you need access to the application services, you can use the getServiceLocator() method, as in the following example:

public function getViewHelperConfig()
{
    return array('factories' => array(
        'foo' => function ($helpers) {
            $services = $helpers->getServiceLocator();
            $someService = $services->get('SomeService');
            $helper = new Helper\Foo($someService);
            return $helper;
        },
    ));
}

This is a powerful technique, as it allows your various plugins to remain agnostic with regards to where and how dependencies are injected, and thus allows you to use Inversion of Control principals even with plugins.