If you want to build professional WordPress plugins—or customize WordPress without touching core files—you must understand hooks. Hooks are the foundation of plugin development and one of the most powerful parts of the WordPress ecosystem.

They allow developers to “hook into” WordPress at specific moments and run custom code without modifying WordPress itself.
This means your plugin or theme stays secure, update-safe, and fully compatible with the platform.

In this complete guide, we’ll break down:

What hooks are
The difference between actions and filters
When to use each type
How priority and parameters work
Real code examples
Tips and best practices
How hooks interact with plugins and themes
How to create your own hooks

By the end, you’ll understand hooks clearly enough to build real-world plugins and extend WordPress safely and efficiently.

What Are WordPress Hooks?

Hooks allow your custom code to interact with WordPress during specific events.

For example:

When a post is saved
When a page loads
When WordPress outputs content
When an admin screen is displayed
When updating settings
When printing scripts
When sending emails
When loading plugins

Hooks make it possible to:

✔ Add new features
✔ Modify existing behavior
✔ Extend plugins and themes
✔ Build commercial products
✔ Remove unwanted defaults

You will use hooks in every plugin you ever build.

Two Types of Hooks

WordPress has two major hook types:

1. Action Hooks

Used to add or run something.

Examples:

Add custom content
Insert a script
Save data
Create admin menus
Trigger background tasks

Syntax:

add_action('hook_name', 'your_function', $priority, $accepted_args);

2. Filter Hooks

Used to modify data before it is displayed or processed.

Examples:

Change titles
Modify excerpts
Edit menu items
Filter content before display
Modify emails

Syntax:

add_filter('hook_name', 'your_function', $priority, $accepted_args);

If you remember only one rule:

👉 Actions do something.
Filters change something.

Understanding Priority and Arguments

Most hooks allow you to set:

Priority

Defines the order in which functions execute.

Example:

add_action('wp_footer', 'my_first_function', 5);
add_action('wp_footer', 'my_second_function', 15);

Lower number = earlier execution.

Accepted Arguments

Hooks can pass data into your function.

Example:

add_filter('the_title', 'modify_title', 10, 2);

function modify_title($title, $post_id) {
    return 'Updated: ' . $title;
}

The 2 means we expect two parameters.

Real Action Hook Examples

Example 1: Add a message to the footer

add_action('wp_footer', function() {
    echo '<p style="text-align:center;">Powered by My Custom Plugin</p>';
});

Example 2: Add a custom admin menu

function mfp_add_admin_menu() {
    add_menu_page(
        'My Plugin Settings',
        'My Plugin',
        'manage_options',
        'mfp-settings',
        'mfp_settings_page_html'
    );
}
add_action('admin_menu', 'mfp_add_admin_menu');

Example 3: Run code when a post is saved

function mfp_save_post($post_id) {
    // your logic here
}
add_action('save_post', 'mfp_save_post');

When to use:

Use action hooks any time you want to execute code.

Real Filter Hook Examples

Example 1: Modify post titles

function mfp_modify_title($title) {
    return '🔥 ' . $title;
}
add_filter('the_title', 'mfp_modify_title');

Example 2: Change excerpt length

function mfp_excerpt_length() {
    return 25;
}
add_filter('excerpt_length', 'mfp_excerpt_length');

Example 3: Add a message at the bottom of content

function mfp_add_content_message($content) {
    if (is_single()) {
        $content .= '<p>Thanks for reading!</p>';
    }
    return $content;
}
add_filter('the_content', 'mfp_add_content_message');

When to use:

Use filters any time you want to modify data.

Where Do Hooks Come From?

Hooks are defined by:

The WordPress core
Themes
Plugins
Your own plugins

For example:

WordPress emits hooks during events:

do_action('init');
do_action('wp_footer');
apply_filters('the_title', $title);

Themes output hooks to allow customization:

<?php do_action('after_header'); ?>

Plugins expose their own hooks so other developers can extend their functionality.

How to Discover Hooks

There are thousands of hooks available.

You can find them:

1. In WordPress Developer Reference

https://developer.wordpress.org/reference/hooks

2. Using a plugin like Query Monitor

Enables real-time inspection of triggered hooks.

3. Searching the WordPress core directory

Look for:

do_action()
apply_filters()

4. Reading plugin/theme documentation

When building professional plugins, reading other plugins’ hook architecture teaches you best practices.

How to Create Your Own Hooks

This is the key to building professional-grade plugins.

Create an action hook

do_action('mfp_after_saving');

Create a filter hook

$value = apply_filters('mfp_modify_value', $value);

When your plugin uses custom hooks, other developers can extend it—this is how large plugins like WooCommerce grow their ecosystem.

Real Example: Custom Hooks in Your Plugin

Let’s say you want to let other developers modify a message.

function mfp_show_message() {
    $message = 'Welcome to my plugin!';
    $message = apply_filters('mfp_message', $message);

    echo esc_html($message);
}

Now other plugins can do:

add_filter('mfp_message', function($text) {
    return '🔥 ' . $text;
});

Congratulations — you just made a plugin extensible.

Commonly Used WordPress Hooks

Here are some of the most important hooks you’ll use repeatedly.

Initialization Hooks

`init`

Runs early, great for:

Custom post types
Shortcodes
Taxonomies

add_action('init', 'mfp_register_features');

Frontend Hooks

`wp_head`

Insert scripts in the page <head>.

add_action('wp_head', 'mfp_meta_tags');

`wp_footer`

Inject content before closing </body>.

Content Hooks

`the_content`

Modify post content.

`the_title`

Change post titles.

Admin Hooks

`admin_menu`

Add settings pages.

`admin_init`

Register settings, fields, and validation.

Saving & Updating Hooks

`save_post`

When a post is saved or updated.

`user_register`

When a new account is created.

E-Commerce Hooks (WooCommerce)

`woocommerce_before_cart`

Add notices or extra scripts above the cart.

`woocommerce_single_product_summary`

Insert content in product pages.

Hook Best Practices for Developers

Using hooks properly takes skill. Here are essential best practices:

1. Always Use Meaningful Function Names

Good:

add_action('init', 'mfp_register_custom_post_types');

Bad:

add_action('init', 'register_stuff');

2. Always Escape Output

Never trust user input:

echo esc_html($message);

3. Always Sanitize Input

$message = sanitize_text_field($_POST['message']);

4. Comment Hook Usage Clearly

Future developers will thank you.

5. Avoid Anonymous Functions for Public Plugins

While closures are convenient, they cannot be removed easily:

remove_action( ... ) // cannot remove closure

Always use named functions for public code.

6. Use Priorities Carefully

Higher priority numbers run later.
Use this to override other plugins if needed.

7. Don’t Overuse Hooks

Hooks are powerful—but too many hooks can make debugging difficult.

Debugging Hooks

Enable WP_DEBUG

define('WP_DEBUG', true);

Use Query Monitor Plugin

Shows:

Which hooks fired
In what order
Their arguments
Execution times

Log Hook Output

error_log('Hook triggered');

Putting It All Together: A Real Plugin Example

Let’s build a simple plugin using multiple hooks.

Plugin Output

Adds an admin page
Saves settings
Displays custom footer message
Allows other developers to modify message via filters

Code

<?php
/**
 * Plugin Name: Custom Footer Message
 */

function cfm_add_admin_menu() {
    add_options_page(
        'Footer Message Settings',
        'Footer Message',
        'manage_options',
        'cfm-settings',
        'cfm_settings_page_html'
    );
}
add_action('admin_menu', 'cfm_add_admin_menu');


function cfm_settings_page_html() {
    ?>
    <div class="wrap">
        <h1>Footer Message Settings</h1>
        <form method="post" action="options.php">
            <?php
            settings_fields('cfm_settings_group');
            do_settings_sections('cfm-settings');
            submit_button();
            ?>
        </form>
    </div>
    <?php
}


function cfm_register_settings() {
    register_setting('cfm_settings_group', 'cfm_message');
}
add_action('admin_init', 'cfm_register_settings');


function cfm_footer_message() {
    $message = get_option('cfm_message', 'Thank you for visiting!');
    $message = apply_filters('cfm_modify_message', $message);
    echo '<p style="text-align:center;">' . esc_html($message) . '</p>';
}
add_action('wp_footer', 'cfm_footer_message');

This example uses:

Action hooks: admin_menu, admin_init, wp_footer
Filter hook: cfm_modify_message
Core functions: register_setting, add_options_page

This is the foundation of real plugin development.

Conclusion

Hooks are one of the most powerful concepts in WordPress. They give developers full control over how and when their code interacts with the platform—without modifying WordPress core.

By understanding actions and filters, you can:

Create plugins
Customize themes
Modify output
Add features
Make your code modular
Build products for clients
Create commercial plugins
Extend other plugins (like WooCommerce)**

Hooks are essential to becoming a professional WordPress developer.

If you master hooks, you master WordPress.

WordPress Hooks Explained: Actions, Filters, and Real Code Examples

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