ADR Knowledge Base

ADR Knowledge Base

Quick reference for Action-Domain-Responder pattern and PHP implementation guidelines.

Core Principles

ADR Components

HTTP Request → Action (collects input)
                 ↓
              Domain (executes business logic)
                 ↓
             Responder (builds HTTP Response)
                 ↓
           HTTP Response

Rule: One action = one HTTP endpoint. Responder builds the COMPLETE response.

Component Responsibilities

ADR vs MVC Comparison

Quick Checklists

Action Checklist

• Single __invoke() method
• No new Response() or response building
• No business logic (if/​switch on domain state)
• Only input parsing and domain invocation
• Returns Responder result

Responder Checklist

• Receives domain result only
• Builds complete HTTP Response
• Handles content negotiation
• Sets status codes based on result
• No domain/​business logic
• No database/​repository access

Domain Checklist

• Same as DDD Domain/​Application layers
• No HTTP/​Response concerns
• Returns domain objects (not HTTP responses)
• Pure business logic

Common Violations Quick Reference

PHP 8.5 ADR Patterns

Action Pattern

<?php

declare(strict_types=1);

namespace Presentation\Api\User\Create;

use Application\User\UseCase\CreateUser\CreateUserUseCase;
use Application\User\UseCase\CreateUser\CreateUserInput;
use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;

final readonly class CreateUserAction
{
    public function __construct(
        private CreateUserUseCase $useCase,
        private CreateUserResponder $responder,
    ) {
    }

    public function __invoke(ServerRequestInterface $request): ResponseInterface
    {
        $input = $this->parseInput($request);
        $result = $this->useCase->execute($input);

        return $this->responder->respond($result);
    }

    private function parseInput(ServerRequestInterface $request): CreateUserInput
    {
        $body = (array) $request->getParsedBody();

        return new CreateUserInput(
            email: $body['email'] ?? '',
            name: $body['name'] ?? '',
        );
    }
}

Responder Pattern

<?php

declare(strict_types=1);

namespace Presentation\Api\User\Create;

use Application\User\UseCase\CreateUser\CreateUserResult;
use Psr\Http\Message\ResponseFactoryInterface;
use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\StreamFactoryInterface;

final readonly class CreateUserResponder
{
    public function __construct(
        private ResponseFactoryInterface $responseFactory,
        private StreamFactoryInterface $streamFactory,
    ) {
    }

    public function respond(CreateUserResult $result): ResponseInterface
    {
        if ($result->isFailure()) {
            return $this->error($result->error());
        }

        return $this->success($result->userId());
    }

    private function success(string $userId): ResponseInterface
    {
        return $this->json(['id' => $userId], 201);
    }

    private function error(string $message): ResponseInterface
    {
        return $this->json(['error' => $message], 400);
    }

    private function json(array $data, int $status): ResponseInterface
    {
        $body = $this->streamFactory->createStream(
            json_encode($data, JSON_THROW_ON_ERROR)
        );

        return $this->responseFactory->createResponse($status)
            ->withHeader('Content-Type', 'application/​json')
            ->withBody($body);
    }
}

Detection Patterns

Action Detection

# Find Action classes
Glob: **/​*Action.php
Glob: **/​Action/​**/​*.php
Grep: "implements.*ActionInterface|extends.*Action" --glob "**/​*.php"

# Detect Action pattern usage
Grep: "public function __invoke.*Request" --glob "**/​*Action.php"

Responder Detection

# Find Responder classes
Glob: **/​*Responder.php
Glob: **/​Responder/​**/​*.php
Grep: "implements.*ResponderInterface" --glob "**/​*.php"

# Detect Responder pattern usage
Grep: "public function respond" --glob "**/​*Responder.php"

Violation Detection

# Response building in Action (Critical)
Grep: "new Response|->withStatus|->withHeader|->withBody" --glob "**/​*Action.php"

# Business logic in Action (Warning)
Grep: "if \(.*->status|switch \(|->isValid\(\)" --glob "**/​*Action.php"

# Domain calls in Responder (Critical)
Grep: "Repository|Service|UseCase" --glob "**/​*Responder.php"

# Multiple public methods in Action (Warning)
Grep: "public function [^_]" --glob "**/​*Action.php" | wc -l

File Structure

Recommended Structure

src/
├── Presentation/
│   ├── Api/
│   │   └── {Context}/
│   │       └── {Action}/
│   │           ├── {Action}Action.php
│   │           ├── {Action}Responder.php
│   │           └── {Action}Request.php (optional DTO)
│   ├── Web/
│   │   └── {Context}/
│   │       └── {Action}/
│   │           ├── {Action}Action.php
│   │           ├── {Action}Responder.php
│   │           └── templates/ (for HTML)
│   └── Shared/
│       ├── Action/
│       │   └── ActionInterface.php
│       └── Responder/
│           └── ResponderInterface.php
├── Application/
│   └── {Context}/
│       └── UseCase/
│           └── {Action}/
│               ├── {Action}UseCase.php
│               ├── {Action}Input.php
│               └── {Action}Result.php
└── Domain/
    └── ...

Alternative Structure (Feature-Based)

src/
├── User/
│   ├── Presentation/
│   │   ├── CreateUser/
│   │   │   ├── CreateUserAction.php
│   │   │   └── CreateUserResponder.php
│   │   └── GetUser/
│   │       ├── GetUserAction.php
│   │       └── GetUserResponder.php
│   ├── Application/
│   │   └── ...
│   └── Domain/
│       └── ...

Integration with DDD

ADR fits naturally with DDD layering:

PSR Integration

ADR works with PSR-7/​PSR-15:

Antipatterns

1. Fat Action (Critical)

// BAD: Action doing too much
class CreateUserAction
{
    public function __invoke(Request $request): Response
    {
        $data = $request->getParsedBody();

        // Validation in Action
        if (empty($data['email'])) {
            return new Response(400, [], 'Email required');
        }

        // Business logic in Action
        $user = new User($data['email']);
        $this->repository->save($user);

        // Response building in Action
        return new Response(201, [], json_encode(['id' => $user->id()]));
    }
}

2. Anemic Responder (Warning)

// BAD: Responder not doing its job
class CreateUserResponder
{
    public function respond($data): Response
    {
        return new Response(200, [], json_encode($data));
    }
}

3. Smart Responder (Critical)

// BAD: Responder with business logic
class CreateUserResponder
{
    public function respond(User $user): Response
    {
        // Domain logic in Responder!
        if ($user->isAdmin()) {
            $this->notificationService->notifyAdmins();
        }

        return $this->json(['id' => $user->id()], 201);
    }
}

References

For detailed information, load these reference files:

• references/​action-patterns.md — Action class patterns and best practices
• references/​responder-patterns.md — Responder class patterns
• references/​domain-integration.md — Integration with DDD Domain layer
• references/​mvc-comparison.md — Detailed MVC vs ADR comparison
• references/​antipatterns.md — Common ADR violations with examples

Assets

• assets/​report-template.md — ADR audit report template