Service Layer Pattern in XOOPS¶

2.5.x ✅ 2026 ✅

Not sure if this is the right pattern?

See Choosing a Data Access Pattern for a decision tree comparing handlers, repositories, services, and CQRS.

Works Today & Tomorrow

The Service Layer pattern works in both XOOPS 2.5.x and 2026. The concepts are universal—only the syntax differs:

Feature	XOOPS 2.5.x	XOOPS 2026
PHP Version	7.4+	8.2+
Constructor Injection	✅ Manual wiring	✅ Container autowiring
Typed Properties	`@var` docblocks	Native type declarations
Readonly Properties	❌ Not available	✅ `readonly` keyword

Code examples below use PHP 8.2+ syntax. For 2.5.x, omit readonly and use traditional property declarations.

The Service Layer Pattern encapsulates business logic in dedicated service classes, providing a clear separation between controllers and data access layers. This pattern promotes code reusability, testability, and maintainability.

Service Layer Concept¶

Purpose¶

The Service Layer: - Contains domain business logic - Coordinates multiple repositories - Handles complex operations - Manages transactions - Performs validation and authorization - Provides high-level operations to controllers

Benefits¶

Reusable business logic across multiple controllers
Easy to test in isolation
Centralized business rule implementation
Clear separation of concerns
Simplified controller code

Dependency Injection¶

<?php
// Service with injected dependencies
class UserService
{
    private $userRepository;
    private $emailService;

    public function __construct(
        UserRepositoryInterface $userRepository,
        EmailServiceInterface $emailService
    ) {
        $this->userRepository = $userRepository;
        $this->emailService = $emailService;
    }

    public function registerUser($username, $email, $password)
    {
        // Validate
        $this->validate($username, $email, $password);

        // Create user
        $user = new User();
        $user->setUsername($username);
        $user->setEmail($email);
        $user->setPassword($password);

        // Save
        $userId = $this->userRepository->save($user);

        // Send welcome email
        $this->emailService->sendWelcome($email, $username);

        return $userId;
    }

    private function validate($username, $email, $password)
    {
        $errors = [];

        if (strlen($username) < 3) {
            $errors['username'] = 'Username too short';
        }

        if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
            $errors['email'] = 'Invalid email';
        }

        if (strlen($password) < 6) {
            $errors['password'] = 'Password too short';
        }

        if (!empty($errors)) {
            throw new ValidationException('Invalid input', $errors);
        }
    }
}
?>

Service Container¶

<?php
class ServiceContainer
{
    private $services = [];

    public function __construct($db)
    {
        // Register repositories
        $this->services['userRepository'] = new UserRepository($db);

        // Register services
        $this->services['userService'] = new UserService(
            $this->services['userRepository']
        );
    }

    public function get($name)
    {
        if (!isset($this->services[$name])) {
            throw new \InvalidArgumentException("Service not found: $name");
        }
        return $this->services[$name];
    }
}
?>

Usage in Controllers¶

<?php
class UserController
{
    private $userService;

    public function __construct(ServiceContainer $container)
    {
        $this->userService = $container->get('userService');
    }

    public function registerAction()
    {
        if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
            return [];
        }

        try {
            $userId = $this->userService->registerUser(
                $_POST['username'],
                $_POST['email'],
                $_POST['password']
            );

            return [
                'success' => true,
                'userId' => $userId,
            ];
        } catch (ValidationException $e) {
            return [
                'success' => false,
                'errors' => $e->getErrors(),
            ];
        }
    }
}
?>

Best Practices¶

Each service handles one domain concern
Services depend on interfaces, not implementations
Use constructor injection for dependencies
Services should be testable in isolation
Throw domain-specific exceptions
Services should not depend on HTTP request details
Keep services focused and cohesive

See also: - MVC-Pattern for controller integration - Repository-Pattern for data access - DTO-Pattern for data transfer objects - Testing for service testing

Tags: #service-layer #business-logic #dependency-injection #design-patterns