Dependency Injection Examples

Constructor.php

<?php

class Notify
{
  /**
   * @var SenderInterface
   */
  protected $sender;

  public function __construct(SenderInterface $sender)
  {
    $this->sender = $sender;
  }

  public function email($message)
  {
    $this->sender->send($message);
  }
}

container.php

<?php

interface ContainerInterface
{
  public function get($name);

  public function set($name, $service);
}

class Container implements ContainerInterface
{
  protected $services = [];

  public function get($name)
  {
    if (!isset($this->services[$name])) {
      return;
    }

    return $this->services[$name];
  }

  public function set($name, $service)
  {
    $this->services[$name] = $service;
  }
}

class Controller
{
  /**
   * @var ContainerInterface
   */
  protected $container;

  public function setContainer(ContainerInterface $container)
  {
    $this->container = $container;
  }

  public function indexAction()
  {
    $render = $this->container->get("render");

    return $render->display("index");
  }
}

factory-with.php

<?php

class Entity
{
}

interface EntityFactoryInterface
{
  public function getEntity($data);
}

class EntityFactory implements EntityFactoryInterface
{
  public function getEntity($data)
  {
    return new Entity($data);
  }
}

class Model
{
  /**
   * @var EntityFactoryInterface
   */
  protected $factory;

  public function __construct(EntityFactory $factory)
  {
    $this->factory = $factory;
  }

  public function getById($id)
  {
    $data = ['id' => 1];
    $entity = $this->factory->getEntity($data);
    return $entity;
  }
}

factory-without.php

<?php

class Entity
{
}

class Model
{
  /**
   * @var Entity
   */
  protected $entity;

  public function __construct(Entity $entity)
  {
    $this->entity = clone $entity;
  }

  public function getById($id)
  {
    $data = ['id' => 1];
    $entity = clone $this->entity;
    $entity->setData($data);
    return $entity;
  }
}

method.php

<?php

class CalendarDay
{
  // ... pretend there is a dependency injection for a database connection.
  public function getDaySchedule(DateTimeInterface $datetime)
  {
    $date = $datetime->format("Y-m-d");

    return $this->connection->prepare(
      "SELECT * FROM `days` WHERE date = ?", $date
    );
  }
}

Setter.php

<?php

class ExampleModel
{
  /**
   * @var ConnectionInterface
   */
  protected $connection;

  public function setConnection(ConnectionInterface $connection)
  {
    $this->connection = $connection;
  }

  public function getAll()
  {
    return $this->connection->query("SELECT * FROM `table`");
  }
}