WordPress Plugin Architecture - Best Practices and Patterns

Building maintainable WordPress plugins requires solid architecture. This guide covers professional plugin architecture patterns, file organization, and best practices for scalable plugin development.

Introduction to Plugin Architecture

Good plugin architecture ensures:

• Maintainability and scalability
• Code reusability
• Easy testing
• Clear separation of concerns
• Professional development standards

Architecture Principles:

• Single Responsibility Principle
• Separation of concerns
• Dependency management
• Proper abstraction layers

Optimal File Structure

Recommended Structure

my-plugin/
├── my-plugin.php          # Main plugin file
├── uninstall.php          # Uninstall handler
├── composer.json          # Dependencies
├── package.json           # Build tools
├── src/
│   ├── Admin/
│   │   ├── Admin.php
│   │   └── Settings.php
│   ├── Frontend/
│   │   └── Frontend.php
│   ├── API/
│   │   └── RestAPI.php
│   ├── Database/
│   │   └── Database.php
│   └── Core/
│       └── Plugin.php
├── includes/
│   └── functions.php
├── assets/
│   ├── css/
│   ├── js/
│   └── images/
└── languages/

Key Directories:

• src/ - Main plugin code (PSR-4 autoloaded)
• includes/ - Helper functions
• assets/ - CSS, JS, images
• languages/ - Translation files

Namespacing and Autoloading

PSR-4 Autoloading

composer.json:

{
  "autoload": {
    "psr-4": {
      "MyPlugin\\": "src/"
    }
  }
}

Main Plugin File:

<?php
namespace MyPlugin;

if (!defined('ABSPATH')) {
    exit;
}

require_once plugin_dir_path(__FILE__) . 'vendor/autoload.php';

class Plugin {
    private static $instance = null;
    
    public static function getInstance() {
        if (null === self::$instance) {
            self::$instance = new self();
        }
        return self::$instance;
    }
    
    private function __construct() {
        $this->init();
    }
    
    private function init() {
        new Admin\Admin();
        new Frontend\Frontend();
        new API\RestAPI();
    }
}

Plugin::getInstance();

Object-Oriented Patterns

Singleton Pattern

For main plugin class:

class Plugin {
    private static $instance = null;
    
    public static function getInstance() {
        if (null === self::$instance) {
            self::$instance = new self();
        }
        return self::$instance;
    }
    
    private function __construct() {
        // Prevent direct instantiation
    }
}

Factory Pattern

For creating related objects:

class ServiceFactory {
    public static function create($service_type) {
        switch ($service_type) {
            case 'api':
                return new API\RestAPI();
            case 'database':
                return new Database\Database();
            default:
                throw new \InvalidArgumentException('Unknown service type');
        }
    }
}

WordPress Hooks System

Organized Hook Registration

class Admin {
    public function __construct() {
        add_action('admin_menu', [$this, 'addMenu']);
        add_action('admin_init', [$this, 'registerSettings']);
        add_filter('plugin_action_links', [$this, 'addActionLinks'], 10, 2);
    }
    
    public function addMenu() {
        add_menu_page(
            'My Plugin',
            'My Plugin',
            'manage_options',
            'my-plugin',
            [$this, 'renderPage']
        );
    }
    
    public function registerSettings() {
        register_setting('my_plugin_settings', 'my_plugin_option');
    }
    
    public function addActionLinks($links, $file) {
        if ($file === plugin_basename(__FILE__)) {
            $links[] = '<a href="' . admin_url('admin.php?page=my-plugin') . '">Settings</a>';
        }
        return $links;
    }
}

Dependency Injection

Constructor Injection

class Service {
    private $database;
    private $logger;
    
    public function __construct(Database $database, Logger $logger) {
        $this->database = $database;
        $this->logger = $logger;
    }
    
    public function doSomething() {
        $this->logger->log('Starting operation');
        $result = $this->database->query('SELECT * FROM table');
        $this->logger->log('Operation complete');
        return $result;
    }
}

Service Container

class Container {
    private $services = [];
    
    public function register($name, $callback) {
        $this->services[$name] = $callback;
    }
    
    public function get($name) {
        if (isset($this->services[$name])) {
            return call_user_func($this->services[$name], $this);
        }
        throw new \Exception("Service {$name} not found");
    }
}

Testing and Quality

Unit Testing Setup

use PHPUnit\Framework\TestCase;

class PluginTest extends TestCase {
    public function testPluginInitializes() {
        $plugin = Plugin::getInstance();
        $this->assertInstanceOf(Plugin::class, $plugin);
    }
}

Code Quality Tools

• PHP_CodeSniffer for coding standards
• PHPStan for static analysis
• PHPUnit for unit testing
• WordPress Coding Standards

Conclusion

Professional plugin architecture requires:

• Proper file organization
• PSR-4 autoloading
• Object-oriented design patterns
• Organized hook registration
• Dependency management
• Testing infrastructure

Following these patterns creates maintainable, scalable WordPress plugins that stand the test of time.