Yii Dependency Injection

PSR-11 compatible dependency injection container that is able to instantiate and configure classes resolving dependencies.

Features

PSR-11 compatible.
Supports property injection, constructor injection and method injection.
Detects circular references.
Accepts array definitions. Could be used with mergeable configs.
Provides autoload fallback for classes without explicit definition.
Allows delegated lookup and has composite container.
Supports aliasing.
Supports service providers and deferred service providers.

Using container

Usage of DI container is fairly simple. First, you initialize it with array of definitions and then objects created according to these are used either in the application directly or to resolve dependencies of other definitions.

Usually a single container is used for the whole application so it is often configured in either entry script such as index.php or a configuration file:

use Yiisoft\Di\Container;

$container = new Container($config);

Config could be stored in a .php file returning array:

return [
    EngineInterface::class => EngineMarkOne::class,
    'full_definition' => [
        '__class' => EngineMarkOne::class,
        '__construct()' => [42], 
        'propertyName' => 'value',
        'setX()' => [42],
    ],
    'closure' => fn (SomeFactory $factory) => $factory->create('args'),
    'static_call_preferred' => fn () => MyFactory::create('args'),
    'static_call_supported' => [MyFactory::class, 'create'],
    'object' => new MyClass(),
];

Interface definition maps an id, that is usually an interface, to particular class.

Full definition describes how to instantiate a class in detail:

__class contains name of the class to be instantiated.
__construct() holds an array of constructor arguments.
The rest of the config and property values and method calls. They are set/called in the order they appear in the array.

Closures are useful if instantiation is tricky and should be described in code. If it is even more complicated, it is a good idea to move such code into a factory and reference it as a static call.

While it is usually not a good idea, you can set already instantiated object into container.

After container is configured, dependencies could be obtained via get():

/** @var \Yiisoft\Di\Container $container */
$object = $container->get('interface_name');

Note, however, that it is a bad practice to use container directly and it is better to rely on autowiring made via Injector available via separate yiisoft/injector pacakge.

Using aliases

Container supports aliases via Reference class. It could be useful to have an ability to retrieve objects both by their interface and named explicitly:

use Yiisoft\Di\Container;

$container = new Container([
    EngineInterface::class => EngineMarkOne::class,
    'engine_one' => EngineInterface::class,
]);

Delegated lookup and composite containers

The Container class supports delegated lookup. When using delegated lookup, all dependencies are always fetched from a given root container. To use delegate lookup you should set root container as a third parameter of the container constructor.

class Car
{
    private EngineInterface $engine;
   
    public function __construct(EngineInterface $engine)
    {
        $this->engine = $engine;
    }
    
    public function getEngine(): EngineInterface
    {
        return $this->engine;
    }
}
$rootContainer = new Container([
    EngineInterface::class => EngineMarkOne::class
]);
$container = new Container([], [], $rootContainer);
$car = $container->get(Car::class);
$engine = $car->getEngine(); //returns an instance of the `Car` class

Composite containers

Composie container allows combining multiple containers into a composite container, which we can then use for lookups. When using this approach, one should only use the composite container.

use Yiisoft\Di\CompositeContainer;
use Yiisoft\Di\Container;

$composite = new CompositeContainer();
$carContainer = new Container([
    EngineInterface::class => EngineMarkOne:class,
    CarInterface::class => Car::class
], []);
$bikeContainer = new Container([
    BikeInterface::class => Bike::class
], []);
$composite->attach($carContainer);
$composite->attach($bikeContainer);
$car = $composite->get(CarInterface::class); //returns an instance of a `Car` class
$bike = $composite->get(BikeInterface::class); //returns an instance of a `Bike` class

Note, containers attached later override dependencies of containers attached earlier.

use Yiisoft\Di\CompositeContainer;
use Yiisoft\Di\Container;

$composite = new CompositeContainer();
$carContainer = new Container([
    EngineInterface::class => EngineMarkOne:class,
    CarInterface::class => Car::class
], []);
$composite->attach($carContainer);
$car = $composite->get(CarInterface::class); //returns an instance of a `Car` class
$engine = $car->getEngine(); //returns an instance of a `EngineMarkOne` class
$engineContainer = new Container([
    EngineInterface::class => EngineMarkTwo:class,
], []);

$composite->attach($engineContainer);
$car = $composite->get(CarInterface::class); //returns an instance of a `Car` class
$engine = $composite->get(EngineInterface::class); //returns an instance of a `EngineMarkTwo` class

A composite container can be a root container for a container delegate lookup.

use Yiisoft\Di\CompositeContainer;
use Yiisoft\Di\Container;

$container = new CompositeContainer();
$container1 = new Container([
    'first' => static function () {
        return 'first';
    },
    'third' => static function () {
        return 'third';
    }
]);
$container2 = new Container([
    'second' => static function () {
        return 'second';
    },
    'first-and-second-and-third' => static function ($c) {
        return $c->get('first') . ' ' . $c->get('second') . ' ' . $c->get('third');
    },
]);

$container->attach($container1);
$container->attach($container2);
$first = $container->get('first'); // returns 'first'
$second = $container->get('second'); // returns 'second'
$firstSecondThird = $container->get('first-and-second-and-third'); //returns 'first second third'

Contextual containers

In an application there are several levels at which we might want to have configuration for the DI container. For example, in Yii application these could be:

An extension providing default configuration
An application with configuration
A module inside the application that uses different configuration than the main application

While in general you never want to inject DI containers into your objects, there are some exceptions such as Yii application modules that need access to the container.

To support this use case while still supporting custom configuration at the module level we have implemented contextual containers. The main class is CompositeContextContainer; it is like CompositeContainer in the sense that it doesn't contain any definitions. The attach() function of the contextual container has an extra string parameter defining the context of the container.

Using context we can create a simple scoping system:

use Yiisoft\Di\Container;
use Yiisoft\Di\CompositeContextContainer;

$composite = new CompositeContextContainer();
$coreContainer = new Container([], []);
$extensionContainer = new Container([], []);

$appContainer = new Container([
    LoggerInterface::class => MainLogger::class
], []);
$moduleAContainer = new Container([
    LoggerInterface::class => LoggerA::class
], []);
$moduleBContainer = new Container([
    LoggerInterface::class => LoggerB::class
], []);

$composite->attach($moduleAContainer, '/moduleA');
$composite->attach($moduleBContainer, '/moduleB');
$composite->attach($appContainer);
$composite->attach($extensionContainer);
$composite->attach($coreContainer);

// The composite context container will allow us to create contextual containers with virtually no overhead.
$moduleAContainer = $composite->getContextContainer('/moduleA');
$moduleBContainer = $composite->getContextContainer('/moduleB');

$composite->get(LoggerInterface::class); // MainLogger
$moduleAContainer->get(LoggerInterface::class); // LoggerA
$moduleBContainer->get(LoggerInterface::class); // LoggerB

Searching is done using the longest prefix first and then checking the containers in the order in which they were added. In case of Yii contextual containers for the modules are created automatically.

Using service providers

A service provider is a special class that responsible for binding complex services or groups of dependencies into the container including registering services with its references, event listeners, middleware etc.

All service providers extend the Yiisoft\Di\Support\ServiceProvider class and contain a register method. Within the register method, you should only bind things into the container. You should never attempt to implement in a service provider any business logic, functionality related to environment bootstrap, functionality that changes DB or anything else than not related to binding things into the container. To access the container in a service provider you should use container field. Container being passed to service provider through constructor and saved to container field.

Typical service provider could look like:

use Yiisoft\Di\Container;
use Yiisoft\Di\Support\ServiceProvider;

class CarFactoryProvider extends ServiceProvider
{
    public function register(Container $container): void
    {
        $this->registerDependencies($container);
        $this->registerService($container);
    }

    protected function registerDependencies(Container $container): void
    {
        $container->set(EngineInterface::class, SolarEngine::class);
        $container->set(WheelInterface::class, [
            '__class' => Wheel::class,
            'color' => 'black',
        ]);
        $container->set(CarInterface::class, [
            '__class' => BMW::class,
            'model' => 'X5',
        ]);
    }

    protected function registerService(Container $container): void
    {
        $container->set(CarFactory::class, [
              '__class' => CarFactory::class,
              'color' => 'red',
        ]);
    }
}

To add service provider to the container you need to pass either service provider class or configuration array as an element of container constructor $providers parameter:

use Yiisoft\Di\Container;

$container = new Container($config, [
    CarFactoryProvider::class,  
]);

Above we created a service provider responsible for bootstrapping of a car factory with all its dependencies. Once a service provider added via configuration array, its register() method is immediately called and services got registered into the container.

Note, service provider might decrease performance of your application if you would perform heavy operations inside the register method.

Using deferred service providers

As stated before, service provider might decrease performance of your application registering heavy services. So to prevent performance decrease you can use so-called deferred service providers.

deferred service providers extend the Yiisoft\Di\Support\DeferredServiceProvider and in addition to register method contain a provides method that returns array with names and identifiers of services service providers bind to the container. Deferred service providers being added to the container the same way as regular service providers but register method of deferred service provider got called only once one of the services listed in provides method is requested from the container. Example:

use Yiisoft\Di\Container;
use Yiisoft\Di\Support\DeferredServiceProvider;

class CarFactoryProvider extends DeferredServiceProvider
{
    public function provides(): array
    {
        return [
            CarFactory::class,
            CarInterface::class,
            EngineInterface::class,
            WheelInterface::class,
        ];
    }
    
    public function register(Container $container): void
    {
        $this->registerDependencies($container);
        $this->registerService($container);
    }

    protected function registerDependencies(Container $container): void
    {
        $container->set(EngineInterface::class, SolarEngine::class);
        $container->set(WheelInterface::class, [
            '__class' => Wheel::class,
            'color' => 'black',
        ]);
        $container->set(CarInterface::class, [
            '__class' => BMW::class,
            'model' => 'X5',
        ]);
    }

    protected function registerService(Container $container): void
    {
        $container->set(CarFactory::class, [
              '__class' => CarFactory::class,
              'color' => 'red',
        ]);
    }
}

$container = new Container($config, [CarFactoryProvider::class]);

// returns false as provider wasn't registered
$container->has(EngineInterface::class); 

// returns SolarEngine, registered in the provider
$engine = $container->get(EngineInterface::class); 

// returns true as provider was registered when EngineInterface was requested from the container
$container->has(EngineInterface::class);

In the code above we added CarFactoryProvider to the container but register method of CarFactoryProvider wasn't executed till EngineInterface was requested from the container. When we requested EngineInterface, container looked at provides list of the CarFactoryProvider and, as EngineInterface is listed in provides, container called register method of the CarFactoryProvider.

Note, you can use deferred service providers not just to defer bootstrap of heavy services but also to register your services to the container only when they are actually needed.

Benchmarks

To run benchmarks execute the next command

composer require phpbench/phpbench $ ./vendor/bin/phpbench run

Note: Only works for php 7.4.

Result example

\Yiisoft\Di\Tests\Benchmark\ContainerBench

benchConstructStupid....................I4 [μ Mo]/r: 438.566 435.190 (μs) [μSD μRSD]/r: 9.080μs 2.07%
benchConstructSmart.....................I4 [μ Mo]/r: 470.958 468.942 (μs) [μSD μRSD]/r: 2.848μs 0.60%
benchSequentialLookups # 0..............R5 I4 [μ Mo]/r: 2,837.000 2,821.636 (μs) [μSD μRSD]/r: 34.123μs 1.20%
benchSequentialLookups # 1..............R1 I0 [μ Mo]/r: 12,253.600 12,278.859 (μs) [μSD μRSD]/r: 69.087μs 0.56%
benchRandomLookups # 0..................R5 I4 [μ Mo]/r: 3,142.200 3,111.290 (μs) [μSD μRSD]/r: 87.639μs 2.79%
benchRandomLookups # 1..................R1 I2 [μ Mo]/r: 13,298.800 13,337.170 (μs) [μSD μRSD]/r: 103.891μs 0.78%
benchRandomLookupsComposite # 0.........R1 I3 [μ Mo]/r: 3,351.600 3,389.104 (μs) [μSD μRSD]/r: 72.516μs 2.16%
benchRandomLookupsComposite # 1.........R1 I4 [μ Mo]/r: 13,528.200 13,502.881 (μs) [μSD μRSD]/r: 99.997μs 0.74%
\Yiisoft\Di\Tests\Benchmark\ContainerMethodHasBench

benchPredefinedExisting.................R1 I4 [μ Mo]/r: 0.115 0.114 (μs) [μSD μRSD]/r: 0.001μs 1.31%
benchUndefinedExisting..................R5 I4 [μ Mo]/r: 0.436 0.432 (μs) [μSD μRSD]/r: 0.008μs 1.89%
benchUndefinedNonexistent...............R5 I4 [μ Mo]/r: 0.946 0.942 (μs) [μSD μRSD]/r: 0.006μs 0.59%
8 subjects, 55 iterations, 5,006 revs, 0 rejects, 0 failures, 0 warnings 
(best [mean mode] worst) = 0.113 [4,483.856 4,486.051] 0.117 (μs) 
⅀T: 246,612.096μs μSD/r 43.563μs μRSD/r: 1.336%

Warning! These summary statistics can be misleading. You should always verify the individual subject statistics before drawing any conclusions.

Legend

μ: Mean time taken by all iterations in variant.

Mo: Mode of all iterations in variant.

μSD: μ standard deviation.

μRSD: μ relative standard deviation.

best: Maximum time of all iterations (minimal of all iterations).

mean: Mean time taken by all iterations.

mode: Mode of all iterations.

worst: Minimum time of all iterations (minimal of all iterations).

Commands examples

Default report for all benchmarks that outputs the result to HTML-file and MD-file

$ ./vendor/bin/phpbench run --report=default --progress=dots --output=md_file --output=html_file

Generated MD-file example

DI benchmark report

suite: 1343b1dc0589cb4e985036d14b3e12cb430a975b, date: 2020-02-21, stime: 16:02:45

benchmark subject set revs iter mem_peak time_rev comp_z_value comp_deviation

ContainerBench benchConstructStupid 0 1000 0 1,416,784b 210.938μs -1.48σ -1.1%

ContainerBench benchConstructStupid 0 1000 1 1,416,784b 213.867μs +0.37σ +0.27%

ContainerBench benchConstructStupid 0 1000 2 1,416,784b 212.890μs -0.25σ -0.18%

ContainerBench benchConstructStupid 0 1000 3 1,416,784b 215.820μs +1.60σ +1.19%

ContainerBench benchConstructStupid 0 1000 4 1,416,784b 212.891μs -0.25σ -0.18%

ContainerBench benchConstructSmart 0 1000 0 1,426,280b 232.422μs -1.03σ -0.5%

ContainerBench benchConstructSmart 0 1000 1 1,426,280b 232.422μs -1.03σ -0.5%

ContainerBench benchConstructSmart 0 1000 2 1,426,280b 233.398μs -0.17σ -0.08%

ContainerBench benchConstructSmart 0 1000 3 1,426,280b 234.375μs +0.69σ +0.33%

ContainerBench benchConstructSmart 0 1000 4 1,426,280b 235.351μs +1.54σ +0.75%

... skipped ... ... ... ... ... ... ... ...

ContainerMethodHasBench benchPredefinedExisting 0 1000 0 1,216,144b 81.055μs -0.91σ -1.19%

ContainerMethodHasBench benchPredefinedExisting 0 1000 1 1,216,144b 83.985μs +1.83σ +2.38%

ContainerMethodHasBench benchPredefinedExisting 0 1000 2 1,216,144b 82.032μs 0.00σ 0.00%

ContainerMethodHasBench benchPredefinedExisting 0 1000 3 1,216,144b 82.031μs 0.00σ 0.00%

ContainerMethodHasBench benchPredefinedExisting 0 1000 4 1,216,144b 81.055μs -0.91σ -1.19%

... skipped ... ... ... ... ... ... ... ...

benchmark	subject	set	revs	iter	mem_peak	time_rev	comp_z_value	comp_deviation
ContainerBench	benchConstructStupid	0	1000	0	1,416,784b	210.938μs	-1.48σ	-1.1%
ContainerBench	benchConstructStupid	0	1000	1	1,416,784b	213.867μs	+0.37σ	+0.27%
ContainerBench	benchConstructStupid	0	1000	2	1,416,784b	212.890μs	-0.25σ	-0.18%
ContainerBench	benchConstructStupid	0	1000	3	1,416,784b	215.820μs	+1.60σ	+1.19%
ContainerBench	benchConstructStupid	0	1000	4	1,416,784b	212.891μs	-0.25σ	-0.18%
ContainerBench	benchConstructSmart	0	1000	0	1,426,280b	232.422μs	-1.03σ	-0.5%
ContainerBench	benchConstructSmart	0	1000	1	1,426,280b	232.422μs	-1.03σ	-0.5%
ContainerBench	benchConstructSmart	0	1000	2	1,426,280b	233.398μs	-0.17σ	-0.08%
ContainerBench	benchConstructSmart	0	1000	3	1,426,280b	234.375μs	+0.69σ	+0.33%
ContainerBench	benchConstructSmart	0	1000	4	1,426,280b	235.351μs	+1.54σ	+0.75%
`... skipped`	`...`	`...`	`...`	`...`	`...`	`...`	`...`	`...`
ContainerMethodHasBench	benchPredefinedExisting	0	1000	0	1,216,144b	81.055μs	-0.91σ	-1.19%
ContainerMethodHasBench	benchPredefinedExisting	0	1000	1	1,216,144b	83.985μs	+1.83σ	+2.38%
ContainerMethodHasBench	benchPredefinedExisting	0	1000	2	1,216,144b	82.032μs	0.00σ	0.00%
ContainerMethodHasBench	benchPredefinedExisting	0	1000	3	1,216,144b	82.031μs	0.00σ	0.00%
ContainerMethodHasBench	benchPredefinedExisting	0	1000	4	1,216,144b	81.055μs	-0.91σ	-1.19%
`... skipped`	`...`	`...`	`...`	`...`	`...`	`...`	`...`	`...`

Legend

benchmark: Benchmark class.

subject: Benchmark class method.

set: Set of data (provided by ParamProvider).

revs: Number of revolutions (represent the number of times that the code is executed).

iter: Number of iteration.

mem_peak: (mean) Peak memory used by iteration as retrieved by memory_get_peak_usage.

time_rev: Mean time taken by all iterations in variant.

comp_z_value: Z-score.

comp_deviation: Relative deviation (margin of error).

Aggregate report for the lookup group that outputs the result to console and MD-file

$ ./vendor/bin/phpbench run --report=aggregate --progress=dots --output=md_file --output=console --group=lookup

Notice

Available groups: construct lookup has