WP hooks introduction

wp-hooks-guide.php

<?php
/**
 * Plugin Name: WP Hooks Guide
 * Description: A guide to WordPress hooks.
 * Version: 1.0
 * Author: Your Name
 * Author URI: http://yourwebsite.com
 * License: GPL2
 * License URI: https://www.gnu.org/licenses/gpl-2.0.html
 * Text Domain: wp-hooks-guide
 *
 * @package WP_Hooks_Guide
 */

// Exit if accessed directly.
if ( ! defined( 'ABSPATH' ) ) {
    exit;
}

/**
 * Example of the following actions and filters in WordPress:
 *
 * add_action()
 * add_filter()
 * do_action()
 * apply_filters()
 */

/**
 * Example of add_action() and do_action().
 *
 * @see https://developer.wordpress.org/reference/functions/add_action/
 * @see https://developer.wordpress.org/reference/functions/do_action/
 */

// Register the custom action
add_action('footer_message', 'wp_hooks_guide_display_message');

function wp_hooks_guide_display_message() {
    echo '<p>Message from the footer!</p>';
}

/**
 * Register custom filter.
 */
add_filter('wp_hooks_guide_filter', 'wp_hooks_guide_filter_callback');
function wp_hooks_guide_filter_callback($content) {
    $original = 'Original content: ' . $content;
    $filtered = 'Filtered content: ' . substr($content, 0, 10);
    return $original . '<br>' . $filtered;
 }

// Fires before the product summary on the single product page.
add_action('woocommerce_before_single_product_summary', 'wp_hooks_guide_display_message');