Here’s an explanation of each of the WordPress core hooks and some practical examples of how they can be used:
- init:
- Syntax:
add_action('init', 'function_name'); - Usage: Used for initialization tasks.
- Practical Example: You can use this hook to register custom post types or taxonomies. For instance, you might register a “Portfolio” post type during initialization.
function custom_post_type_registration() {
// Register a custom post type
register_post_type('portfolio', $args);
}
add_action('init', 'custom_post_type_registration');
- wp_head:
- Syntax:
add_action('wp_head', 'function_name'); - Usage: Outputs content in the
<head>section of a WordPress site. This is commonly used for adding custom styles or scripts. - Practical Example: Adding a custom CSS stylesheet to the
<head>.
function custom_styles() {
echo '<link rel="stylesheet" type="text/css" href="' . get_template_directory_uri() . '/custom.css" />';
}
add_action('wp_head', 'custom_styles');
- wp_footer:
- Syntax:
add_action('wp_footer', 'function_name'); - Usage: Outputs content just before the closing
</body>tag, often used for adding JavaScript or analytics code. - Practical Example: Adding a Google Analytics tracking code.
function google_analytics() {
echo '<script async src="https://www.googletagmanager.com/gtag/js?id=GA_MEASUREMENT_ID"></script>';
echo '<script>';
echo ' window.dataLayer = window.dataLayer || [];';
echo ' function gtag(){dataLayer.push(arguments);}';
echo ' gtag("js", new Date());';
echo ' gtag("config", "GA_MEASUREMENT_ID");';
echo '</script>';
}
add_action('wp_footer', 'google_analytics');
- the_content:
- Syntax: N/A
- Usage: Allows modification of post content before it’s displayed. You typically use it by creating a filter function.
- Practical Example: Adding a custom text before the post content.
function custom_content_modifier($content) {
return 'Custom Text: ' . $content;
}
add_filter('the_content', 'custom_content_modifier');
- wp_enqueue_scripts:
- Syntax:
add_action('wp_enqueue_scripts', 'function_name'); - Usage: Used for enqueuing scripts and styles on the frontend.
- Practical Example: Enqueueing a custom JavaScript file.
function enqueue_custom_scripts() {
wp_enqueue_script('custom-script', get_template_directory_uri() . '/custom.js', array('jquery'), '1.0', true);
}
add_action('wp_enqueue_scripts', 'enqueue_custom_scripts');
- wp_login and wp_logout:
- Syntax:
add_action('wp_login', 'function_name');andadd_action('wp_logout', 'function_name'); - Usage: Fired when a user logs in and logs out, respectively.
- Practical Example: Sending an email notification upon user login or logout.
function send_login_notification($username) {
// Send an email notification or log the event
}
add_action('wp_login', 'send_login_notification');
function send_logout_notification($username) {
// Send an email notification or log the event
}
add_action('wp_logout', 'send_logout_notification');
- save_post:
- Syntax:
add_action('save_post', 'function_name'); - Usage: Triggered when a post is saved or updated.
- Practical Example: Automatically generating a custom excerpt for a post upon saving.
function generate_excerpt($post_id) {
if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) return;
$post_content = get_post_field('post_content', $post_id);
$excerpt = substr(strip_tags($post_content), 0, 200) . '...';
update_post_meta($post_id, '_excerpt', $excerpt);
}
add_action('save_post', 'generate_excerpt');
- template_redirect:
- Syntax:
add_action('template_redirect', 'function_name'); - Usage: Used for redirecting templates or handling custom redirects.
- Practical Example: Redirecting certain user roles to a custom page.
function custom_template_redirect() {
if (is_user_logged_in() && current_user_can('subscriber')) {
wp_redirect(home_url('/custom-page'));
exit;
}
}
add_action('template_redirect', 'custom_template_redirect');
- after_setup_theme:
- Syntax:
add_action('after_setup_theme', 'function_name'); - Usage: Runs after the theme is set up, often used for theme-specific configurations.
- Practical Example: Adding support for featured images.
function theme_setup() {
add_theme_support('post-thumbnails');
}
add_action('after_setup_theme', 'theme_setup');
- wp_title:
- Syntax:
add_filter('wp_title', 'function_name'); - Usage: This hook is used to modify the title of a WordPress page. It allows you to customize the text that appears in the
<title>tag of the HTML document. - Practical Example: Adding a custom prefix to page titles. For instance, if the original page title is “About Us,” you can modify it to “Custom Prefix: About Us.”
function custom_page_title($title) {
return 'Custom Prefix: ' . $title;
}
add_filter('wp_title', 'custom_page_title');
- plugins_loaded:
- Syntax:
add_action('plugins_loaded', 'function_name'); - Usage: This hook is fired when WordPress loads plugins. It’s typically used for early plugin initialization tasks, such as defining constants, setting up configuration options, or initializing custom functionality.
- Practical Example: Initializing custom plugins or settings. You can use this hook to ensure that your custom plugin code is loaded at an early stage.
function custom_plugin_init() {
// Your plugin initialization code here
}
add_action('plugins_loaded', 'custom_plugin_init');
- admin_init and admin_menu:
- Syntax:
add_action('admin_init', 'function_name');andadd_action('admin_menu', 'function_name'); - Usage: These hooks are used for tasks related to the WordPress admin panel.
admin_initis fired during the initialization of the admin area, andadmin_menuis used to add items to the admin menu. - Practical Example: Adding a custom admin menu page. In this example, we create a custom menu page named “Custom Menu” under the admin menu.
function custom_admin_menu() {
add_menu_page('Custom Page', 'Custom Menu', 'manage_options', 'custom-menu', 'custom_menu_page');
}
function custom_menu_page() {
// Content for the custom admin menu page
}
add_action('admin_menu', 'custom_admin_menu');
- widgets_init:
- Syntax:
add_action('widgets_init', 'function_name'); - Usage: This hook is used for registering widgets in WordPress. Widgets are small blocks of content that can be placed in widgetized areas, such as sidebars or footers.
- Practical Example: Registering a custom widget for your theme. In this example, we register a custom sidebar widget area called “Custom Sidebar.”
function custom_widgets_init() {
register_sidebar(array(
'name' => 'Custom Sidebar',
'id' => 'custom-sidebar',
'description' => 'This is a custom widget area.',
'before_widget' => '<div class="widget">',
'after_widget' => '</div>',
'before_title' => '<h2 class="widget-title">',
'after_title' => '</h2>',
));
}
add_action('widgets_init', 'custom_widgets_init');
These hooks are essential for extending and customizing the functionality of WordPress, allowing developers to add their own code at specific points in the WordPress lifecycle to tailor the behavior and appearance of their websites or plugins.