Various examples of Dependency Injection done right using Zend Framework's ServiceManager and Psr\Container

BarService.php

<?php

namespace Application\Service;

use DateTime;

class BarService
{
    protected $dateTime;
  
    public function __construct(DateTime $dateTime)
    {
        $this->dateTime = $dateTime;
    }
}

BarServiceFactory.php

<?php

namespace Application\Factory\Service;

use Application\Service\BarService;
use DateTime;
use Psr\Container\ContainerInterface;

class BarServiceFactory
{
    /**
     * @param ContainerInterface $container
     * @return BarService
     */
    public function __invoke(ContainerInterface $container)
    {
        return new BarService(new DateTime());
    }
}

FooController.php

<?php

namespace Application\Controller;

use Application\Form\FooForm;
use Zend\Mvc\Controller\AbstractActionController;

final class FooController extends AbstractActionController
{
    /** @var FooForm */
    private $form;
    
    /** @var FooService */
    private $fooService;

    public function __construct(FooForm $fooForm, FooService $fooService)
    {
        $this->form = $fooForm;
        $this->fooService = $fooService;
    }
}

FooControllerFactory.php

<?php

namespace Application\Factory\Controller;

use Psr\Container\ContainerInterface;
use Application\Controller\FooController;
use Application\Form\FooForm;

final class FooControllerFactory
{
    public function __invoke(ContainerInterface $container): FooController
    {
        // TODO: Remove this line if this is a Factory for a Service or you've upgraded to ServiceManager ^3.0
        /** @var ContainerInterface $container */
        $container = $container->getServiceLocator();

        return new FooController(
            $container->get('FormElementManager')->get(FooForm::class),
            $container->get('SomeAlias') // SomeAlias is an alias to Application\Service\FooService::class
        );
    }
}

FooForm.php

<?php

namespace Application\Form;

use Zend\Form\Form;
use Zend\InputFilter\InputFilterProviderInterface;

final class FooForm extends Form implements InputFilterProviderInterface
{
    public function init() 
    {
        $this->add([
            'name' => 'foo',
        ]);
    }
    /**
     * Should return an array specification compatible with
     * {@link Zend\InputFilter\Factory::createInputFilter()}.
     *
     * @return array
     */
    public function getInputFilterSpecification(): array
    {
        return [
            'foo' => [
                'required' => true,
            ],
        ];
    }
}

FooService.php

<?php

namespace Application\Service;

class FooService
{
    protected $barService;
    protected $invokableService;
  
    public function __construct(
        BarService $barService, 
        InvokableService $invokableService
    ) {
        $this->barService = $barService;
        $this->invokableService = $invokableService;
    }
}

FooServiceFactory.php

<?php

namespace Application\Factory\Service;

use Application\Service\BarService;
use Application\Service\FooService;
use Application\Service\InvokableService;
use Psr\Container\ContainerInterface;

class FooServiceFactory
{
    /**
     * @param ContainerInterface $container
     * @return FooService
     */
    public function __invoke(ContainerInterface $container): FooService
    {
        return new FooService(
            $container->get(BarService::class),
            $container->get(InvokableService::class)
        );
    }
}

InvokableService.php

<?php

namespace Application\Service;

class InvokableService
{
  
}

module.config.php

<?php

use Application\Controller;
use Application\Factory;
use Application\Form;
use Application\Service;
use Zend\ServiceManager\Factory\InvokableFactory;

return [
    'controllers' => [
        'factories' => [
            Controller\FooController::class => Factory\Controller\FooControllerFactory::class,
        ],
    ],
    'form_elements' => [
        'factories' => [
            Form\FooForm::class => InvokableFactory::class,
        ],
    ],
    'service_manager' => [
        'factories'  => [
            Service\FooService::class       => Factory\Service\FooServiceFactory::class,
            Service\BarService::class       => Factory\Service\BarServiceFactory::class,
            Service\InvokableService::class => InvokableFactory::class,
        ],
        'aliases' => [
            'SomeAlias' => Service\FooService::class,
        ],
    ],
];