README.md

PHP Dependency Injection Container

A simple and lightweight dependency injection container built in PHP, compliant with PSR-11 standards. This container is designed for binding values and creating objects, automatically resolving any dependencies they require.

Usage

Initialise the container

First create an instance of the container.

<?php

use Memuya\Container\Container;

$container = new Container();

You can also create a new instance and retrieve it via:

<?php
use Memuya\Container\Container;

$container = Container::getInstance();

Bind to container

You can bind a key to both simple and complex values to the container.

<?php
// Scalar/primitive type.
$container->bind('key', fn (): string => 'Hello, world!');

// Object.
$container->bind('someObject', function (): \stdClass {
  $object = new \stdClass();
  $object->name = 'Bob';

  return $object;
});

Check if binding exist

To see if a binding already exists in the container, you can use the has() method.

$container->has('key'); // true
$container->has('doesNotExist'); // false

Retrieve value from container

<?php

$key = $container->get('key');
$someObject = $container->get('someObject');

If a key does not exists, the container will throw a NotFoundException exception. This exception implements the Psr\Container\NotFoundExceptionInterface interface.

<?php

use Memuya\Container\Exceptions\NotFoundException;

try {
  $key = $container->get('doesNotExist');
} catch (NotFoundException $e) {
  echo $ex->getMessage(); // 'doesNotExist' not found in container
}

Each time an object is retrieved from the container, it will re-create it fresh. If you require the object be binded as a singleton, you can use the singleton() method inplace of bind().

$container->singleton('someObject', function (): \stdClass {
  $object = new \stdClass();
  $object->name = 'Bob';

  return $object;
});

This will give you back the exact same object every time as it is resolved when the binding is initiated.

You can then check if a binding is a singleton with the isSingleton() method.

$container->isSingleton('key'); // false
$container->isSingleton('someObject'); // true

Alias

If required, you can alias an already existing key in the container to another key.

$container->alias('key', 'aliasKey');

$container->get('key'); // Hello, world
$container->get('aliasKey'); // Hello, world

Removing binding

If you no longer require a binding in the container, you may remove it with the remove() method.

$container->remove('key');
$container->get('key'); // Throws a NotFoundException exception.

Creating objects and resolving their dependencies

The container can also be used to create and resolve objects and their dependencies automatically. If a class or its dependencies cannot be resolved, a ContainerException will be thrown.

Take the below as an example, where we have class A which has class B as a dependency.

<?php

class A
{
  public function __construct(private B $b) {}

  public function sayHello(): string
  {
    return $this->b->greet();
  }
}

class B
{
  public function greet(): string
  {
    return 'Hello!';
  }
}

You can leverage the container to built class A and resolve it's dependency B.

use Memuya\Container\Exceptions\ContainerException;

try {
  $a = $container->make(A::class);
  $a->sayHello(); // Hello!
} catch (ContainerException $ex) {

}