Clean Code Principles for XOOPS

Overview

Clean code is code that is easy to read, understand, and maintain. This guide covers clean code principles specifically applied to XOOPS module development.

Core Principles

mindmap
  root((Clean Code))
    Readability
      Meaningful Names
      Small Functions
      Comments When Needed
    Simplicity
      Single Responsibility
      DRY Principle
      KISS Principle
    Maintainability
      Consistent Style
      Error Handling
      Testing

Meaningful Names

Variables

// Bad
$d = new DateTime();
$u = $memberHandler->getUser($id);
$arr = [];

// Good
$createdDate = new DateTime();
$currentUser = $memberHandler->getUser($userId);
$publishedArticles = [];

Functions

// Bad
function process($data) { ... }
function handle($item) { ... }
function doStuff($x, $y) { ... }

// Good
function publishArticle(Article $article): void { ... }
function calculateTotalPrice(array $items): float { ... }
function sendNotificationEmail(User $user, string $subject): bool { ... }

Classes

// Bad
class Manager { ... }
class Helper { ... }
class Utils { ... }

// Good
class ArticleRepository { ... }
class NotificationService { ... }
class PermissionChecker { ... }

Small Functions

Single Responsibility

// Bad - does too many things
function processArticle($data) {
    // Validate
    if (empty($data['title'])) {
        throw new Exception('Title required');
    }
    // Save
    $article = new Article();
    $article->setTitle($data['title']);
    $this->repository->save($article);
    // Notify
    $this->mailer->send($article->getAuthor(), 'Article published');
    // Log
    $this->logger->info('Article created');
    return $article;
}

// Good - each function does one thing
function validateArticleData(array $data): void
{
    if (empty($data['title'])) {
        throw new ValidationException('Title required');
    }
}

function createArticle(array $data): Article
{
    $this->validateArticleData($data);
    return Article::create($data['title'], $data['content']);
}

function publishArticle(Article $article): void
{
    $this->repository->save($article);
    $this->notifyAuthor($article);
    $this->logArticleCreation($article);
}

Function Length

Keep functions short - ideally under 20 lines:

// Good - focused function
public function getPublishedArticles(int $limit = 10): array
{
    $criteria = new CriteriaCompo();
    $criteria->add(new Criteria('status', 'published'));
    $criteria->setSort('published_at');
    $criteria->setOrder('DESC');
    $criteria->setLimit($limit);

    return $this->repository->getObjects($criteria);
}

DRY Principle (Don’t Repeat Yourself)

Extract Common Code

// Bad - repeated code
function getActiveUsers() {
    $criteria = new CriteriaCompo();
    $criteria->add(new Criteria('level', 0, '>'));
    $criteria->setSort('uname');
    return $this->userHandler->getObjects($criteria);
}

function getActiveAdmins() {
    $criteria = new CriteriaCompo();
    $criteria->add(new Criteria('level', 0, '>'));
    $criteria->add(new Criteria('is_admin', 1));
    $criteria->setSort('uname');
    return $this->userHandler->getObjects($criteria);
}

// Good - shared logic extracted
function getUsers(CriteriaCompo $criteria): array
{
    $criteria->add(new Criteria('level', 0, '>'));
    $criteria->setSort('uname');
    return $this->userHandler->getObjects($criteria);
}

function getActiveUsers(): array
{
    return $this->getUsers(new CriteriaCompo());
}

function getActiveAdmins(): array
{
    $criteria = new CriteriaCompo();
    $criteria->add(new Criteria('is_admin', 1));
    return $this->getUsers($criteria);
}

Error Handling

Use Exceptions Properly

// Bad - generic exceptions
throw new Exception('Error');

// Good - specific exceptions
throw new ArticleNotFoundException($articleId);
throw new PermissionDeniedException('Cannot edit article');
throw new ValidationException(['title' => 'Title is required']);

Handle Errors Gracefully

public function findArticle(string $id): ?Article
{
    try {
        return $this->repository->findById($id);
    } catch (DatabaseException $e) {
        $this->logger->error('Database error finding article', [
            'id' => $id,
            'error' => $e->getMessage()
        ]);
        throw new ServiceException('Unable to retrieve article', 0, $e);
    }
}

Comments

When to Comment

// Bad - obvious comment
// Increment counter
$counter++;

// Good - explains why, not what
// Cache for 1 hour to reduce database load during peak traffic
$cache->set($key, $data, 3600);

// Good - documents complex algorithm
/**
 * Calculate article relevance score using TF-IDF algorithm.
 * Higher scores indicate better match with search terms.
 */
function calculateRelevanceScore(Article $article, array $terms): float
{
    // ...
}

Code Organization

Class Structure

class ArticleService
{
    // 1. Constants
    private const MAX_TITLE_LENGTH = 255;

    // 2. Properties
    private ArticleRepository $repository;
    private EventDispatcher $events;

    // 3. Constructor
    public function __construct(
        ArticleRepository $repository,
        EventDispatcher $events
    ) {
        $this->repository = $repository;
        $this->events = $events;
    }

    // 4. Public methods
    public function publish(Article $article): void { ... }
    public function archive(Article $article): void { ... }

    // 5. Private methods
    private function validateForPublication(Article $article): void { ... }
}

Clean Code Checklist

• Names are meaningful and pronounceable
• Functions do one thing only
• Functions are small (< 20 lines)
• No duplicated code
• Proper error handling with specific exceptions
• Comments explain “why”, not “what”
• Consistent formatting and style
• No magic numbers or strings
• Dependencies are injected, not created

Related Documentation

• Code Organization
• Error Handling
• Testing Best Practices
• PHP Standards