Object-Oriented PHP

Class and Instance

final class MyPlugin_Assets {
    public function register(): void {
        add_action('wp_enqueue_scripts', [$this, 'enqueue']);
    }

    public function enqueue(): void {
        wp_enqueue_style('myplugin', MYPLUGIN_URL . 'assets/frontend.css', [], MYPLUGIN_VERSION);
    }
}

$assets = new MyPlugin_Assets();
$assets->register();

Visibility

Visibility	Meaning
public	Accessible anywhere
protected	Accessible in class and subclasses
private	Accessible only in class

Constructor

final class Repository {
    private wpdb $db;

    public function __construct(wpdb $db) {
        $this->db = $db;
    }
}

Typed properties require PHP 7.4+. Constructor property promotion requires PHP 8+.

Static Methods

final class Formatter {
    public static function price(float $amount): string {
        return '$' . number_format($amount, 2);
    }
}

Formatter::price(10.5);

Use static methods for stateless helpers, not hidden global state.

Inheritance, Interfaces, Traits, Enums

interface RendererInterface {
    public function render(array $data): string;
}

trait HasSettings {
    protected function get_settings(): array {
        return get_option('myplugin_settings', []);
    }
}

enum Layout: string {
    case Grid = 'grid';
    case List = 'list';
}

Enums require PHP 8.1+.

WordPress OOP Hook Pattern

final class MyPlugin_Settings_Page {
    public function register(): void {
        add_action('admin_menu', [$this, 'add_page']);
    }

    public function add_page(): void {
        add_options_page(
            __('My Plugin', 'my-plugin'),
            __('My Plugin', 'my-plugin'),
            'manage_options',
            'my-plugin',
            [$this, 'render']
        );
    }

    public function render(): void {
        echo '<div class="wrap"><h1>' . esc_html__('My Plugin', 'my-plugin') . '</h1></div>';
    }
}

Dependency Injection

final class ReportController {
    public function __construct(private ReportRepository $repository) {}
}

$controller = new ReportController(new ReportRepository());
$controller->register();

Manual wiring is usually enough for small and medium plugins.

Practical Class Boundaries

Class Type	Good Responsibility
Assets	Enqueue scripts and styles
SettingsPage	Register and render settings screens
RestController	Register routes and handle REST requests
Repository	Read and write data
Renderer	Convert normalized data to HTML
Synchronizer	Coordinate external API sync

Common OOP Pitfalls in WordPress

• One giant plugin class that handles every feature.
• Hook registration hidden inside constructors.
• Excessive abstraction around simple WordPress APIs.
• Static state that makes tests and request behavior hard to predict.
• Using modern PHP syntax on unsupported servers.
• Forgetting that hooks need callable methods.