CODESAMPLE

Layered Architecture - PHP

Layered Architecture PHP

The Layered Architecture pattern organizes an application into distinct layers, each with a specific responsibility. This separation concerns allows for easier maintenance, testing, and modification – changes in one layer ideally don’t affect others. Common layers include Presentation (UI), Application (Business Logic), and Data (Data Access).

My PHP implementation showcases these layers. The Presentation layer (handled through a simple controller) receives input and displays output. The Application layer (UserService) encapsulates business rules regarding users. The Data layer (UserRepository) is responsible for database interactions. Dependency Injection is used to connect the layers, promoting loose coupling and testability – making this implementation a standard approach in many PHP frameworks.

<?php

// Data Layer: UserRepository
class UserRepository {
    private $db;

    public function __construct($db) {
        $this->db = $db; // Assume $db is a PDO connection
    }

    public function getAllUsers(): array {
        $stmt = $this->db->query("SELECT * FROM users");
        return $stmt->fetchAll(PDO::FETCH_ASSOC);
    }

    public function getUserById(int $id): ?array {
        $stmt = $this->db->prepare("SELECT * FROM users WHERE id = :id");
        $stmt->bindParam(':id', $id, PDO::PARAM_INT);
        $stmt->execute();
        return $stmt->fetch(PDO::FETCH_ASSOC);
    }
}

// Application Layer: UserService
class UserService {
    private $userRepository;

    public function __construct(UserRepository $userRepository) {
        $this->userRepository = $userRepository;
    }

    public function getAllUsers(): array {
        return $this->userRepository->getAllUsers();
    }

    public function getUserById(int $id): ?array {
        return $this->userRepository->getUserById($id);
    }
}

// Presentation Layer: UserController
class UserController {
    private $userService;

    public function __construct(UserService $userService) {
        $this->userService = $userService;
    }

    public function index(): void {
        $users = $this->userService->getAllUsers();
        // In a real application, this would render a view (e.g., using Blade)
        echo "<pre>";
        print_r($users);
        echo "</pre>";
    }

    public function show(int $id): void {
        $user = $this->userService->getUserById($id);
        // In a real application, this would render a view
        echo "<pre>";
        print_r($user);
        echo "</pre>";
    }
}

// Setup (for demonstration purposes)
try {
    $db = new PDO('sqlite::memory:');
    $db->exec("CREATE TABLE users (id INTEGER PRIMARY KEY, name TEXT)");
    $db->exec("INSERT INTO users (name) VALUES ('Alice')");
    $db->exec("INSERT INTO users (name) VALUES ('Bob')");

    $userRepository = new UserRepository($db);
    $userService = new UserService($userRepository);
    $userController = new UserController($userService);

    $userController->index(); // List all users
    $userController->show(1);  // Show user with ID 1

} catch (PDOException $e) {
    echo "Database error: " . $e->getMessage();
}