Advanced WordPress Development

Chapter 4: Plugin Development

4.1 Plugin Structure

Create well-structured WordPress plugins.

<?php
/**
 * Plugin Name: My Custom Plugin
 * Plugin URI: https://example.com/plugin
 * Description: Custom plugin description
 * Version: 1.0.0
 * Author: Your Name
 */

// Prevent direct access
if (!defined('ABSPATH')) {
    exit;
}

// Plugin code here
?>

4.2 Plugin Activation and Deactivation

Handle plugin activation and deactivation hooks.

// Activation hook
register_activation_hook(__FILE__, 'my_plugin_activate');

function my_plugin_activate() {
    // Create database tables
    // Set default options
    // Flush rewrite rules
}

// Deactivation hook
register_deactivation_hook(__FILE__, 'my_plugin_deactivate');

function my_plugin_deactivate() {
    // Clean up temporary data
    // Flush rewrite rules
}

4.3 Plugin Settings Page

Create admin settings pages for plugins.

// Add settings menu
add_action('admin_menu', 'my_plugin_settings_menu');

function my_plugin_settings_menu() {
    add_options_page(
        'My Plugin Settings',
        'My Plugin',
        'manage_options',
        'my-plugin-settings',
        'my_plugin_settings_page'
    );
}

function my_plugin_settings_page() {
    // Settings page HTML
}

4.4 Plugin Security Best Practices

Secure your plugins from vulnerabilities.

• Sanitize Input: Use sanitize_text_field, sanitize_email
• Validate Data: Check data before using
• Escape Output: Use esc_html, esc_attr, esc_url
• Nonces: Verify form submissions
• Capabilities: Check user permissions

4.5 Plugin Internationalization

Make plugins translatable.

// Load text domain
load_plugin_textdomain('my-plugin', false, dirname(plugin_basename(__FILE__)) . '/languages');

// Use translation functions
__('Text to translate', 'my-plugin');
_e('Text to echo', 'my-plugin');
esc_html__('Text to escape', 'my-plugin');