Theory of Operation
Getting an MVC application configured and ready to dispatch has
required an increasing amount of code as more features become
available: setting up the database, configuring your view and view
helpers, configuring your layouts, registering plugins, registering
action helpers, and more.
Additionally, you will often want to reuse the same code to
bootstrap your tests, a cronjob, or a service script. While it's
possible to simply include your bootstrap script, oftentimes there
are initializations that are environment specific – you may not need
the MVC for a cronjob, or just the DB layer for a service script.
Zend_Application aims to make this easier and to
promote reuse by encapsulating bootstrapping into OOP paradigms.
Zend_Application is broken into three realms:
Zend_Application: loads the PHP
environment, including include_paths and autoloading, and instantiates
the requested bootstrap class.
Zend_Application_Bootstrap: provides
interfaces for bootstrap classes.
Zend_Application_Bootstrap_Bootstrap provides common
functionality for most bootstrapping needs, including
dependency checking algorithms and the ability to load
bootstrap resources on demand.
Zend_Application_Resource provides an
interface for standard bootstrapping resources that can be
loaded on demand by a bootstrap instance, as well as several
default resource implementations.
Developers create a bootstrap class for their application, extending
Zend_Application_Bootstrap_Bootstrap or implementing (minimally)
Zend_Application_Bootstrap_Bootstrapper. The entry point
(e.g., public/index.php) will load
Zend_Application, and instantiate it by passing:
The current environment
Options for bootstrapping
The bootstrap options include the path to the file containing the
bootstrap class and optionally:
Any extra include_paths to set
Any additional autoloader namespaces to register
Any php.ini settings to initialize
The class name for the bootstrap class (if not "Bootstrap")
Resource prefix to path pairs to use
Any resources to use (by class name or short name)
Additional path to a configuration file to load
Additional configuration options
Options may be an array, a Zend_Config object, or the path
to a configuration file.
BootstrappingZend_Application's second area of responsibility is
executing the application bootstrap. Bootstraps minimally need to
implement Zend_Application_Bootstrap_Bootstrapper,
which defines the following API:
This API allows the bootstrap to accept the environment and
configuration from the application object, report the resources its
responsible for bootstrapping, and then bootstrap and run the
application.
You can implement this interface on your own, extend
Zend_Application_Bootstrap_BootstrapAbstract, or use
Zend_Application_Bootstrap_Bootstrap.
Besides this functionality, there are a number of other areas of
concern you should familiarize yourself with.
Resource Methods
The Zend_Application_Bootstrap_BootstrapAbstract
implementation provides a simple convention for defining class
resource methods. Any protected method beginning with a name
prefixed with _init will be considered a resource
method.
To bootstrap a single resource method, use the
bootstrap() method, and pass it the name of the
resource. The name will be the method name minus the
_init prefix.
To bootstrap several resource methods, pass an array of names.
Too bootstrap all resource methods, pass nothing.
Take the following bootstrap class:
To bootstrap just the _initFoo() method, do the
following:
bootstrap('foo');
]]>
To bootstrap the _initFoo() and
_initBar() methods, do the following:
bootstrap(array('foo', 'bar'));
]]>
To bootstrap all resource methods, call bootstrap()
with no arguments:
bootstrap();
]]>Bootstraps that use resource plugins
To make your bootstraps more re-usable, we have provided the
ability to push your resources into resource plugin classes.
This allows you to mix and match resources simply via
configuration. We will cover how
to create resources later; in
this section we will show you how to utilize them only.
If your bootstrap should be capable of using resource plugins,
you will need to implement an additional interface,
Zend_Application_Bootstrap_ResourceBootstrapper.
This interface defines an API for locating, registering, and
loading resource plugins:
Resource plugins basically provide the ability to create
resource intializers that can be re-used between applications.
This allows you to keep your actual bootstrap relatively clean,
and to introduce new resources without needing to touch your
bootstrap itself.
Zend_Application_Bootstrap_BootstrapAbstract (and
Zend_Application_Bootstrap_Bootstrap by extension)
implement this interface as well, allowing you to utilize
resource plugins.
To utilize resource plugins, you must specify them in the
options passed to the application object and/or bootstrap. These
options may come from a configuration file, or be passed in
manually. Options will be of key to options pairs, with the key
representing the resource name. The resource name will be the
segment following the class prefix. For example, the resources
shipped with Zend Framework have the class prefix
"Zend_Application_Resource_"; anything following this would
be the name of the resource. As an example,
array(
'FrontController' => array(
'controllerDirectory' => APPLICATION_PATH . '/controllers',
),
),
));
]]>
This indicates that the "FrontController" resource should be
used, with the options specified.
If you begin writing your own resource plugins, or utilize
third-party resource plugins, you will need to tell your
bootstrap where to look for them. Internally, the bootstrap
utilizes Zend_Loader_PluginLoader, so you will only
need to indicate the common class prefix an path pairs.
As an example, let's assume you have custom resource plugins in
APPLICATION_PATH/resources/ and that they share the
common class prefix of My_Resource. You would then
pass that information to the application object as follows:
array(
'My_Resource' => APPLICATION_PATH . '/resources/',
),
'resources' => array(
'FrontController' => array(
'controllerDirectory' => APPLICATION_PATH . '/controllers',
),
),
));
]]>
You would now be able to use resources from that directory.
Just like resource methods, you use the bootstrap()
method to execute resource plugins. Just like with resource
methods, you can specify either a single resource plugin,
multiple plugins (via an array), or all plugins. Additionally,
you can mix and match to execute resource methods as well.
bootstrap('FrontController');
// Execute several:
$bootstrap->bootstrap(array('FrontController', 'Foo'));
// Execute all resource methods and plugins:
$bootstrap->bootstrap();
]]>Resource Registry
Many, if not all, of your resource methods or plugins will
initialize objects, and in many cases, these objects will be
needed elsewhere in your application. How can you access them?
Zend_Application_Bootstrap_BootstrapAbstract
provides a local registry for these objects. To store your
objects in them, you simply return them from your resources.
For maximum flexibility, this registry is referred to as a
"container" internally; its only requirements are that it is an
object. Resources are then registered as properties named after
the resource name. By default, an instance of
Zend_Registry is used, but you may also specify any
other object you wish. The methods setContainer()
and getContainer() may be used to manipulate the
container itself. getResource($resource) can be
used to fetch a given resource from the container, and
hasResource($resource) to check if the resource has
actually been registered.
As an example, consider a basic view resource:
You can then check for it and/or fetch it as follows:
hasResource('view')) {
$view = $bootstrap->getResource('view');
}
// Via the container:
$container = $bootstrap->getContainer();
if (isset($container->view)) {
$view = $container->view;
}
]]>
Please note that the registry and also the container is not global. This
means that you need access to the bootstrap in order to fetch
resources. Zend_Application_Bootstrap_Bootstrap
provides some convenience for this: during its
run() execution, it registers itself as the front
controller parameter "bootstrap", which allows you to fetch it
from the router, dispatcher, plugins, and action controllers.
As an example, if you wanted access to the view resource from
above within your action controller, you could do the following:
getInvokeArg('bootstrap');
$view = $bootstrap->getResource('view');
// ...
}
}
]]>Dependency Tracking
In addition to executing resource methods and plugins, it's
necessary to ensure that these are executed once and once
only; these are meant to bootstrap an application, and
executing multiple times can lead to resource overhead.
At the same time, some resources may depend on other
resources being executed. To solve these two issues,
Zend_Application_Bootstrap_BootstrapAbstract
provides a simple, effective mechanism for dependency
tracking.
As noted previously, all resources -- whether methods or plugins
-- are bootstrapped by calling bootstrap($resource),
where $resource is the name of a resource, an array
of resources, or, left empty, indicates all resources should be
run.
If a resource depends on another resource, it should call
bootstrap() within its code to ensure that resource
has been executed. Subsequent calls to it will then be ignored.
In a resource method, such a call would look like this:
bootstrap('FrontController');
// Retrieve the front controller from the bootstrap registry
$front = $this->getResource('FrontController');
$request = new Zend_Controller_Request_Http();
$request->setBaseUrl('/foo');
$front->setRequest($request);
// Ensure the request is stored in the bootstrap registry
return $request;
}
}
]]>Resource Plugins
As noted
previously, a good way to create re-usable bootstrap resources and to
offload much of your coding to discrete classes is to utilize resource
plugins. While Zend Framework ships with a number of standard
resource plugins, the intention is that developers should write
their own to encapsulate their own initialization needs.
Resource plugins need only implement
Zend_Application_Resource_Resource, or, more simply
still, extend
Zend_Application_Resource_ResourceAbstract. The basic
interface is simply this:
The interface defines simply that a resource plugin should accept options
to the constructor, have mechanisms for setting and retrieving
options, have mechanisms for setting and retrieving the bootstrap
object, and an initialization method.
As an example, let's assume you have a common view intialization you
use in your applications. You have a common doctype, CSS and
JavaScript, and you want to be able to pass in a base document title
via configuration. Such a resource plugin might look like this:
getView();
}
public function getView()
{
if (null === $this->_view) {
$options = $this->getOptions();
$title = '';
if (array_key_exists('title', $options)) {
$title = $options['title'];
unset($options['title']);
}
$view = new Zend_View($options);
$view->doctype('XHTML1_STRICT');
$view->headTitle($title);
$view->headLink()->appendStylesheet('/css/site.css');
$view->headScript()->appendfile('/js/analytics.js');
$viewRenderer =
Zend_Controller_Action_HelperBroker::getStaticHelper(
'ViewRenderer'
);
$viewRenderer->setView($view);
$this->_view = $view;
}
return $this->_view;
}
}
]]>
As long as you register the prefix path for this resource plugin,
you can then use it in your application. Even better, because it
uses the plugin loader, you are effectively overriding the shipped
"View" resource plugin, ensuring that your own is used instead.