비즈니스 로직과 데이터 액세스를 분리하는 데 있어 PHP 함수의 역할

class Database {
    private $host;
    private $user;
    private $password;
    private $database;
    private $connection;

    public function __construct($host, $user, $password, $database) {
        $this->host = $host;
        $this->user = $user;
        $this->password = $password;
        $this->database = $database;

        $this->connect();
    }

    private function connect() {
        $this->connection = new PDO("mysql:host=$this->host;dbname=$this->database", $this->user, $this->password);
    }

    public function executeQuery($sql) {
        $statement = $this->connection->prepare($sql);
        $statement->execute();

        return $statement->fetchAll(PDO::FETCH_ASSOC);
    }
}

class UserModel {
    private $database;

    public function __construct(Database $database) {
        $this->database = $database;
    }

    public function getAllUsers() {
        $sql = "SELECT * FROM users";

        return $this->database->executeQuery($sql);
    }

    public function getUserById($id) {
        $sql = "SELECT * FROM users WHERE id = :id";

        $statement = $this->database->connection->prepare($sql);
        $statement->bindParam(":id", $id);
        $statement->execute();

        return $statement->fetch(PDO::FETCH_ASSOC);
    }
}

class UserController {
    private $userModel;

    public function __construct(UserModel $userModel) {
        $this->userModel = $userModel;
    }

    public function index() {
        $users = $this->userModel->getAllUsers();

        return view('index', ['users' => $users]);
    }

    public function show($id) {
        $user = $this->userModel->getUserById($id);

        return view('show', ['user' => $user]);
    }
}

use App\Http\Controllers\UserController;

Route::get('/', [UserController::class, 'index']);
Route::get('/users/{id}', [UserController::class, 'show']);