Action hooks in Wordpress - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an action hook in WordPress?

An action hook is a way to add or change functionality in WordPress by running custom code at specific points during WordPress execution.

beginner

How do you add a function to an action hook in WordPress?

Use the add_action('hook_name', 'your_function_name'); function to tell WordPress to run your function when the hook runs.

intermediate

What is the difference between an action hook and a filter hook?

An action hook runs code at certain points but does not change data. A filter hook lets you modify data before it is used or displayed.

intermediate

What parameters can add_action accept besides the hook name and function?

It can accept priority (number to control order) and number of accepted arguments (how many inputs your function expects).

beginner

Give an example of a common WordPress action hook and its use.

The wp_footer action hook runs just before the closing </body> tag. You can use it to add scripts or HTML to the footer.

Which function is used to attach a function to an action hook in WordPress?

A add_action

B add_filter

C do_action

D apply_filters

add_action attaches your function to an action hook. add_filter is for filters, do_action runs the hook, and apply_filters runs filters.

What does the priority parameter in add_action control?

A The type of hook (action or filter)

B How many arguments your function accepts

C The number of times your function runs

D The order your function runs compared to others on the same hook

Priority controls the order functions run on the same hook. Lower numbers run first.

When is an action hook typically executed?

A At specific points during WordPress execution

B Only when a user logs in

C When a post is published

D Only during plugin activation

Action hooks run at many points in WordPress, like loading the header, footer, or saving a post.

Which hook would you use to add code just before the closing </body> tag?

A init

B wp_head

C wp_footer

D admin_init

wp_footer runs before the closing </body> tag, perfect for footer scripts.

What happens if you call do_action('my_hook') in your code?

A It creates a new hook named 'my_hook'

B All functions attached to 'my_hook' run in order

C It removes all functions from 'my_hook'

D It returns the value of 'my_hook'

do_action runs all functions attached to the named action hook.

Explain what an action hook is and how you use it in WordPress.

Think about how WordPress lets you add your code at certain points.

Describe the difference between action hooks and filter hooks in WordPress.

One changes behavior, the other changes data.

Practice

1. What is the main purpose of an action hook in WordPress?

easy

A. To create new database tables automatically

B. To let you add custom code at specific points without changing core files

C. To style the website using CSS

D. To replace WordPress themes entirely

Solution

1. Step 1: Understand what action hooks do

   Action hooks allow you to insert your own code at certain points in WordPress execution.

2. Step 2: Recognize safe customization

   This lets you customize WordPress without editing its core files, which is safer and update-proof.

3. Final Answer:

   To let you add custom code at specific points without changing core files -> Option B

4. Quick Check:

   Action hooks = safe custom code insertion [OK]

Hint: Action hooks add code safely without core file changes [OK]

Common Mistakes:

• Thinking action hooks create database tables
• Confusing action hooks with styling tools
• Believing action hooks replace themes

2. Which of the following is the correct syntax to add a function to an action hook in WordPress?

easy

A. add_action('init', my_function());

B. add_action(my_function, 'init');

C. add_action('init', 'my_function');

D. add_action('my_function', init);

Solution

1. Step 1: Recall add_action syntax

   The first argument is the hook name as a string, the second is the function name as a string.

2. Step 2: Check each option

   add_action('init', 'my_function'); matches the correct syntax: add_action('hook_name', 'function_name'); others mix argument order or call the function immediately.

3. Final Answer:

   add_action('init', 'my_function'); -> Option C

4. Quick Check:

   Hook name first, function name second as strings [OK]

Hint: Hook name and function name are strings in add_action() [OK]

Common Mistakes:

• Swapping hook and function arguments
• Passing function call instead of function name
• Not using quotes around function name

3. What will be the output of this code snippet?

function greet() {
  echo 'Hello!';
}
add_action('wp_footer', 'greet');

Assuming the theme calls do_action('wp_footer'); in the footer.

medium

A. The text 'Hello!' will appear in the footer

B. Nothing will be displayed

C. A PHP error will occur

D. The text 'greet' will appear in the footer

Solution

1. Step 1: Understand add_action and do_action

   add_action attaches 'greet' function to 'wp_footer' hook. When do_action('wp_footer') runs, it calls 'greet'.

2. Step 2: Analyze the greet function output

   The greet function echoes 'Hello!', so this text will appear where the footer hook runs.

3. Final Answer:

   The text 'Hello!' will appear in the footer -> Option A

4. Quick Check:

   do_action triggers greet, which echoes 'Hello!' [OK]

Hint: do_action runs hooked functions, output appears where called [OK]

Common Mistakes:

• Thinking nothing happens without explicit call
• Confusing function name string with output
• Expecting errors from correct hook usage

4. Identify the error in this code snippet:

function add_custom_text() {
  echo 'Custom Text';
}
add_action('init', add_custom_text());

medium

A. The function add_custom_text is not defined

B. The hook name 'init' is invalid

C. Missing semicolon after function definition

D. The function add_custom_text is called immediately instead of being hooked

Solution

1. Step 1: Check how add_action expects arguments

   add_action expects the second argument as a function name string, not a function call.

2. Step 2: Identify the mistake in the code

   Using add_custom_text() calls the function immediately and passes its result, which is incorrect.

3. Final Answer:

   The function add_custom_text is called immediately instead of being hooked -> Option D

4. Quick Check:

   Pass function name as string, not call it [OK]

Hint: Use function name string, not function call in add_action() [OK]

Common Mistakes:

• Calling function instead of passing name
• Assuming hook name is wrong
• Missing semicolon confusion

5. You want to add a custom message only after the WordPress footer content is fully loaded, but only on single post pages. Which code snippet correctly uses an action hook with a condition?

hard

A. add_action('wp_footer', function() { if (is_single()) { echo 'Thanks for reading!'; } });

B. add_action('init', function() { if (is_single()) { echo 'Thanks for reading!'; } });

C. add_action('wp_head', function() { if (is_single()) { echo 'Thanks for reading!'; } });

D. add_action('wp_footer', function() { echo 'Thanks for reading!'; });

Solution

1. Step 1: Identify the correct hook for footer output

   'wp_footer' runs after footer content loads, so it's the right hook to add footer messages.

2. Step 2: Apply condition to show message only on single posts

   Using is_single() inside the hooked function ensures the message appears only on single post pages.

3. Final Answer:

   add_action('wp_footer', function() { if (is_single()) { echo 'Thanks for reading!'; } }); -> Option A

4. Quick Check:

   Footer hook + condition inside function = correct usage [OK]

Hint: Use wp_footer hook with is_single() condition inside function [OK]

Common Mistakes:

• Using init or wp_head hooks for footer content
• Not adding condition for single posts
• Echoing outside hooked function