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 optional autoload fallback for classes without explicit definition.
• Allows delegated lookup and has composite container.
• Supports aliasing.
• Supports service providers.
• Has state resetter for long-running workers serving multiple requests such as RoadRunner or Swoole.
• Supports container delegates.

Requirements

• PHP 7.4 or higher.
• Multibyte String PHP extension.

Installation

The package could be installed with composer:

composer require yiisoft/di --prefer-dist

Using the container

Usage of the DI container is fairly simple: You first initialize it with an array of definitions. The array keys are usually interface names. It will then use these definitions to create an object whenever that type is requested. This happens for example when fetching a type directly from the container somewhere in the application. But objects are also created implicitly if a definition has a dependency to another definition.

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

use Yiisoft\Di\Container;
use Yiisoft\Di\ContainerConfig;

$config = ContainerConfig::create()
    ->withDefinitions($definitions);

$container = new Container($config);

The definitions could be stored in a .php file that returns an 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(),
];

As seen above an object can be defined in several ways:

• In the simple case an interface definition maps an id to a particular class.
• A full definition describes how to instantiate a class in more detail:
  • class contains the name of the class to be instantiated.
  • __construct() holds an array of constructor arguments.
  • The rest of the config are property values (prefixed with $) and method calls, postfixed with (). They are set/called in the order they appear in the array.
• Closures are useful if instantiation is tricky and can better be described in code. When using these, arguments are auto-wired by type. ContainerInterface could be used to get current container instance.
• 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 also set an already instantiated object into the container.

See yiisoft/definitions for more information.

After the container is configured, a service can be obtained via get():

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

Note, however, that it is bad practice using a container directly. It is much better to rely on autowiring as provided by the Injector available from the yiisoft/injector package.

Using aliases

The DI container supports aliases via the Yiisoft\Definitions\Reference class. This way objects can also be retrieved by a more handy name:

use Yiisoft\Di\Container;
use Yiisoft\Di\ContainerConfig;

$config = ContainerConfig::create()
    ->withDefinitions([
        EngineInterface::class => EngineMarkOne::class,
        'engine_one' => EngineInterface::class,
    ]);

$container = new Container($config);
$object = $container->get('engine_one');

Composite containers

A composite container combines multiple containers in a single container. When using this approach, objects should only be fetched from the composite container.

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

$composite = new CompositeContainer();

$carConfig = ContainerConfig::create()
    ->withDefinitions([
        EngineInterface::class => EngineMarkOne::class,
        CarInterface::class => Car::class
    ]);
$carContainer = new Container($carConfig);

$bikeConfig = ContainerConfig::create()
    ->withDefinitions([
        BikeInterface::class => Bike::class
    ]);

$bikeContainer = new Container($bikeConfig);
$composite->attach($carContainer);
$composite->attach($bikeContainer);

// Returns an instance of a `Car` class.
$car = $composite->get(CarInterface::class);
// Returns an instance of a `Bike` class.
$bike = $composite->get(BikeInterface::class);

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

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

$carConfig = ContainerConfig::create()
    ->withDefinitions([
        EngineInterface::class => EngineMarkOne::class,
        CarInterface::class => Car::class
    ]);

$carContainer = new Container($carConfig);

$composite = new CompositeContainer();
$composite->attach($carContainer);

// Returns an instance of a `Car` class.
$car = $composite->get(CarInterface::class);
// Returns an instance of a `EngineMarkOne` class.
$engine = $car->getEngine();

$engineConfig = ContainerConfig::create()
    ->withDefinitions([
        EngineInterface::class => EngineMarkTwo::class,
    ]);

$engineContainer = new Container($engineConfig);

$composite = new CompositeContainer();
$composite->attach($engineContainer);
$composite->attach($carContainer);

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

Using service providers

A service provider is a special class that is responsible for providing complex services or groups of dependencies for the container and extensions of existing services.

A provider should extend from Yiisoft\Di\ServiceProviderInterface and must contain a getDefinitions() and getExtensions() methods. It should only provide services for the container and therefore should only contain code that is related to this task. It should never implement any business logic or other functionality such as environment bootstrap or applying changes to database.

A typical service provider could look like:

use Yiisoft\Di\Container;
use Yiisoft\Di\ServiceProviderInterface;

class CarFactoryProvider extends ServiceProviderInterface
{
    public function getDefinitions(): array
    {
        return [
            CarFactory::class => [
                'class' => CarFactory::class,
                '$color' => 'red',
            ], 
            EngineInterface::class => SolarEngine::class,
            WheelInterface::class => [
                'class' => Wheel::class,
                '$color' => 'black',
            ],
            CarInterface::class => [
                'class' => BMW::class,
                '$model' => 'X5',
            ],
        ];    
    }
     
    public function getExtensions(): array
    {
        return [
            // Note that Garage should already be defined in container 
            Garage::class => function(ContainerInterface $container, Garage $garage) {
                $car = $container
                    ->get(CarFactory::class)
                    ->create();
                $garage->setCar($car);
                
                return $garage;
            }
        ];
    } 
}

Here we created a service provider responsible for bootstrapping of a car factory with all its dependencies.

An extension is a callable that returns a modified service object. In our case we get existing Garage service and put a car into the garage by calling the method setCar(). Thus, before applying this provider, we had an empty garage and with the help of the extension we fill it.

To add this service provider to a container you can pass either its class or a configuration array in the additional config:

use Yiisoft\Di\Container;
use Yiisoft\Di\ContainerConfig;

$config = ContainerConfig::create()
    ->withProviders([CarFactoryProvider::class]);

$container = new Container($config);

When a service provider is added, its getDefinitions() and getExtensions() methods are called immediately both services and their extensions get registered into the container.

Container tags

You can tag services in the following way:

use Yiisoft\Di\Container;
use Yiisoft\Di\ContainerConfig;

$config = ContainerConfig::create()
    ->withDefinitions([  
        BlueCarService::class => [
            'class' => BlueCarService::class,
            'tags' => ['car'], 
        ],
        RedCarService::class => [
            'definition' => fn () => new RedCarService(),
            'tags' => ['car'],
        ],
    ]);

$container = new Container($config);

Now we can get tagged services from the container in the following way:

$container->get('tag@car');

The result is an array that contains two instances: BlueCarService and RedCarService.

Another way to tag services is setting tags via container constructor:

use Yiisoft\Di\Container;
use Yiisoft\Di\ContainerConfig;

$config = ContainerConfig::create()
    ->withDefinitions([  
        BlueCarService::class => [
            'class' => BlueCarService::class,
        ],
        RedCarService::class => fn () => new RedCarService(),
    ])
    ->withTags([
        // "car" tag has references to both blue and red cars
        'car' => [BlueCarService::class, RedCarService::class]
    ]);

$container = new Container($config);

Resetting services state

Despite stateful services is not a great practice, these are inevitable in many cases. When you build long-running applications with tools like Swoole or RoadRunner you should reset the state of such services every request. For this purpose you can use StateResetter with resetters callbacks:

$resetter = new StateResetter();
$resetter->setResetters([
    MyServiceInterface::class => function () {
        $this->reset(); // a method of MyServiceInterface
    },
]);

The callback has access to the private and protected properties of the service instance, so you can set initial state of the service efficiently without creating a new instance.

The reset itself should be triggered after each request-response cycle. For RoadRunner it would look like the following:

while ($request = $psr7->acceptRequest()) {
    $response = $application->handle($request);
    $psr7->respond($response);
    $application->afterEmit($response);
    $container
        ->get(\Yiisoft\Di\StateResetter::class)
        ->reset();
    gc_collect_cycles();
}

Setting resetters in definitions

Reset state is defined for each individual service by providing "reset" callback in the following way:

use Yiisoft\Di\Container;
use Yiisoft\Di\ContainerConfig;

$config = ContainerConfig::create()
    ->withDefinitions([
        EngineInterface::class => EngineMarkOne::class,
        EngineMarkOne::class => [
            'class' => EngineMarkOne::class,
            'setNumber()' => [42],
            'reset' => function () {
                $this->number = 42;
            },
        ],
    ]);

$container = new Container($config);

Note: resetters from definitons work only if you don't set StateResetter in definition or service providers.

Configuring StateResetter manually

To manually add resetters or in case you use Yii DI composite container with a third party container that does not support state reset natively, state resetter could be configured separately. The following example is PHP-DI:

MyServiceInterface::class => function () {
    // ...
},
StateResetter::class => function () {
    $resetter = new StateResetter();
    $resetter->setResetters([
        MyServiceInterface::class => function () {
            $this->reset(); // a method of MyServiceInterface
        },
    ]);
    return $resetter;
}

Specifying metadata for non-array definitions

In order to specify some metadata, such as in cases of "resetting services state" or "container tags" above, for non-array definitions, the following syntax could be used:

LogTarget::class => [
    'definition' => static function (LoggerInterface $logger) use ($params) {
        $target = ...
        return $target;
    },
    'reset' => function () use ($params) {
        ...
    },
],

In the above we have explicitly moved definition itself to "definition" key.

Delegates

Container delegates define. Each delegate is a callable returning a container instance that is used in case a service can not be found in primary container:

function (ContainerInterface $container): ContainerInterface
{

}

In order to configure delegates use additional config:

use Yiisoft\Di\Container;
use Yiisoft\Di\ContainerConfig;

$config = ContainerConfig::create()
    ->withDelegates([
        function (ContainerInterface $container): ContainerInterface {
            // ...
        }
    ]);


$container = new Container($config);

Tuning for production

By default, the container validates definitions right when they are set. In production environment, it makes sense to turn it off:

use Yiisoft\Di\Container;
use Yiisoft\Di\ContainerConfig;

$config = ContainerConfig::create()
    ->withValidate(false);

$container = new Container($config);

Strict mode

Container may work in strict mode, i.e. when everything in the container should be defined explicitly. In order to turn it on use the following code:

use Yiisoft\Di\Container;
use Yiisoft\Di\ContainerConfig;

$config = ContainerConfig::create()
    ->withStrictMode(true);

$container = new Container($config);

Further reading

• Martin Fowler's article.

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).

Command examples

• Default report for all benchmarks that outputs the result to CSV-file

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

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 CSV-file

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

Notice

Available groups: construct lookup has

Generated MD-file example

DI benchmark report

suite: 1343b1d2654a3819c72a96d236302b70a504dac7, date: 2020-02-21, stime: 13:27:32

benchmark	subject	set	revs	its	mem_peak	best	mean	mode	worst	stdev	rstdev	diff
ContainerBench	benchSequentialLookups	0	1000	5	1,454,024b	168.945μs	170.117μs	169.782μs	171.875μs	0.957μs	0.56%	1.00x
ContainerBench	benchSequentialLookups	1	1000	5	1,445,296b	3,347.656μs	3,384.961μs	3,390.411μs	3,414.062μs	21.823μs	0.64%	19.90x
ContainerBench	benchSequentialLookups	2	1000	5	1,445,568b	3,420.898μs	3,488.477μs	3,447.260μs	3,657.227μs	85.705μs	2.46%	20.51x
ContainerBench	benchRandomLookups	0	1000	5	1,454,024b	169.922μs	171.875μs	171.871μs	173.828μs	1.381μs	0.80%	1.01x
ContainerBench	benchRandomLookups	1	1000	5	1,445,296b	3,353.515μs	3,389.844μs	3,377.299μs	3,446.289μs	31.598μs	0.93%	19.93x
ContainerBench	benchRandomLookups	2	1000	5	1,445,568b	3,445.313μs	3,587.696μs	3,517.823μs	3,749.023μs	115.850μs	3.23%	21.09x
ContainerBench	benchRandomLookupsComposite	0	1000	5	1,454,032b	297.852μs	299.610μs	298.855μs	302.734μs	1.680μs	0.56%	1.76x
ContainerBench	benchRandomLookupsComposite	1	1000	5	1,445,880b	3,684.570μs	3,708.984μs	3,695.731μs	3,762.695μs	28.297μs	0.76%	21.80x
ContainerBench	benchRandomLookupsComposite	2	1000	5	1,446,152b	3,668.946μs	3,721.680μs	3,727.407μs	3,765.625μs	30.881μs	0.83%	21.88x

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).
• its: Number of iterations (one measurement for each iteration).
• mem_peak: (mean) Peak memory used by each iteration as retrieved by memory_get_peak_usage.
• best: Maximum time of all iterations in variant.
• mean: Mean time taken by all iterations in variant.
• mode: Mode of all iterations in variant.
• worst: Minimum time of all iterations in variant.
• stdev: Standard deviation.
• rstdev: The relative standard deviation.
• diff: Difference between variants in a single group.

Testing

Unit testing

The package is tested with PHPUnit. To run tests:

./vendor/bin/phpunit

Mutation testing

The package tests are checked with Infection mutation framework with Infection Static Analysis Plugin. To run it:

./vendor/bin/roave-infection-static-analysis-plugin

Static analysis

The code is statically analyzed with Psalm. To run static analysis:

./vendor/bin/psalm

License

The Yii Dependency Injection is free software. It is released under the terms of the BSD License. Please see LICENSE for more information.

Maintained by Yii Software.

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