README

Basic Service Container implementation providing psr/container-implementation.

Also known as Dependency Injection Container or Service Locator.

See PSR-11 for more information.

Use case

Step 1: define a list of rules to create objects of needed types

<?php

// services.php

namespace Vertilia\Container;

return [
    // instantiating via callback
    EnvMockInterface::class => function () {
        return new EnvMock();
    },

    // instantiating via array of service names
    ServiceMock::class => [EnvMockInterface::class],

    // instantiating via callback with additional params allowed
    'ServiceMockAlias' => function (...$args) {
        return new ServiceMock($this->get(EnvMockInterface::class), ...$args);
    },

    // returning existing object
    'ServiceMockObject' => (object) 'test string',

    // returning string value
    'ServiceMockString' => 'test string',

    // returning other scalar value
    'ServiceMockInt' => 42,
];

Here you may use some different formats to specify how objects of specific classes will be created:

1. instantiating via callback. Defines a callback that will return a new object instance. In our example when we'll ask for the EnvMockInterface we will receive an instance of EnvMock

2. instantiating via array of service names. If object creation needs a list of other objects for its constructor, we provide their names in an array. This way container will first instantiate these dependencies and then will call the class constructor passing dependencies as parameters. In our case the container will proceed in the following way:

   return new ServiceMock(new EnvMock); (here EnvMockInterface::class dependency will be resolved by a previous rule).

3. instantiating via callback with additional params allowed. Same callback than in the first rule, but with additional arguments. Use this form when specific objects need additional arguments to pass into constructor. You can specify a fixed number of arguments or use php-5.6 specific ... operator.

4. it is also possible to just return existing objects and even scalars, as shown in 3 last examples.

You can have as many rule files as needed, so each module in your application may come with its own descriptions.

Step 2: instantiate ServiceContainer with the list of rule files

<?php

// bootstrap.php

$app = new \Vertilia\Container\ServiceContainer([__DIR__ . '/services.php']);

You may now ask the $app service container to return you the object of needed class. It will take all the necessary actions to find it in its store or create it if necessary.

$svc = $app->get(\Vertilia\Container\ServiceMock::class);

print_r($svc->env);

Please see more usage cases in tests/.

Final note

Service Containers together with Dependency Injection techniques do a great job to remove singletons from our applications, help decouple our code, make it more testable and SOLID.