andreaskweber / pimple

A small PHP 5.3 dependency injection container

Pimple

Caution

This is the documentation for Pimple 3.x. If you are using Pimple 1.x, read the Pimple 1.x documentation. Reading the Pimple 1.x code is also a good way to learn more about how to create a simple Dependency Injection Container (recent versions of Pimple are more focused on performance).

Pimple is a small Dependency Injection Container for PHP.

Installation

Before using Pimple in your project, add it to your composer.json file:

$ ./composer.phar require pimple/pimple ~3.0

Alternatively, Pimple is also available as a PHP C extension:

$ git clone https://github.com/silexphp/Pimple
$ cd Pimple/ext/pimple
$ phpize
$ ./configure
$ make
$ make install

Usage

Creating a container is a matter of creating a Container instance:

use Pimple\Container;

$container = new Container();

As many other dependency injection containers, Pimple manages two different kind of data: services and parameters.

Defining Services

A service is an object that does something as part of a larger system. Examples of services: a database connection, a templating engine, or a mailer. Almost any global object can be a service.

Services are defined by anonymous functions that return an instance of an object:

// define some services
$container['session_storage'] = function ($c) {
    return new SessionStorage('SESSION_ID');
};

$container['session'] = function ($c) {
    return new Session($c['session_storage']);
};

Notice that the anonymous function has access to the current container instance, allowing references to other services or parameters.

As objects are only created when you get them, the order of the definitions does not matter.

Using the defined services is also very easy:

// get the session object
$session = $container['session'];

// the above call is roughly equivalent to the following code:
// $storage = new SessionStorage('SESSION_ID');
// $session = new Session($storage);

Defining Factory Services

By default, each time you get a service, Pimple returns the same instance of it. If you want a different instance to be returned for all calls, wrap your anonymous function with the factory() method

$container['session'] = $container->factory(function ($c) {
    return new Session($c['session_storage']);
});

Now, each call to $container['session'] returns a new instance of the session.

Defining Parameters

Defining a parameter allows to ease the configuration of your container from the outside and to store global values:

// define some parameters
$container['cookie_name'] = 'SESSION_ID';
$container['session_storage_class'] = 'SessionStorage';

If you change the session_storage service definition like below:

$container['session_storage'] = function ($c) {
    return new $c['session_storage_class']($c['cookie_name']);
};

You can now easily change the cookie name by overriding the session_storage_class parameter instead of redefining the service definition.

Protecting Parameters

Because Pimple sees anonymous functions as service definitions, you need to wrap anonymous functions with the protect() method to store them as parameters:

$container['random_func'] = $container->protect(function () {
    return rand();
});

Modifying Services after Definition

In some cases you may want to modify a service definition after it has been defined. You can use the extend() method to define additional code to be run on your service just after it is created:

$container['session_storage'] = function ($c) {
    return new $c['session_storage_class']($c['cookie_name']);
};

$container->extend('session_storage', function ($storage, $c) {
    $storage->...();

    return $storage;
});

The first argument is the name of the service to extend, the second a function that gets access to the object instance and the container.

Extending a Container

If you use the same libraries over and over, you might want to reuse some services from one project to the next one; package your services into a provider by implementing Pimple\ServiceProviderInterface:

use Pimple\Container;

class FooProvider implements Pimple\ServiceProviderInterface
{
    public function register(Container $pimple)
    {
        // register some services and parameters
        // on $pimple
    }
}

Then, register the provider on a Container:

$pimple->register(new FooProvider());

Fetching the Service Creation Function

When you access an object, Pimple automatically calls the anonymous function that you defined, which creates the service object for you. If you want to get raw access to this function, you can use the raw() method:

$container['session'] = function ($c) {
    return new Session($c['session_storage']);
};

$sessionFunction = $container->raw('session');