Action hooks in Wordpress - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What happens when this WordPress action hook runs?

Consider the following code snippet added to a WordPress theme's functions.php file. What will be the output on the page when the 'wp_footer' action runs?

Wordpress

<?php
add_action('wp_footer', function() {
    echo '<p>Footer message</p>';
});
?>

A Nothing appears because 'wp_footer' is not a valid action hook.

B A PHP error occurs because anonymous functions cannot be used with add_action.

C The text '<p>Footer message</p>' appears at the bottom of the page inside the footer section.

D The text appears at the top of the page before the header.

💡 Hint

Think about where the 'wp_footer' hook is triggered in a WordPress theme.

The 'wp_footer' action hook is triggered just before the closing tag in most WordPress themes. Adding a function to this hook outputs content at the bottom of the page.

📝 Syntax

intermediate

Which option correctly adds a function to a WordPress action hook?

You want to run a function named 'my_custom_function' when the 'init' action hook fires. Which code snippet correctly does this?

A add_action(my_custom_function, 'init');

B add_action('init', 'my_custom_function');

C add_action('init', my_custom_function());

D add_action('init', function my_custom_function() {});

💡 Hint

Remember the order of parameters for add_action is hook name, then function name as a string.

The correct syntax is add_action('hook_name', 'function_name_as_string'). Option B follows this pattern.

🔧 Debug

advanced

Why does this action hook not run the function?

Look at this code snippet. The function 'add_custom_message' is not running when expected. What is the cause?

Wordpress

<?php
function add_custom_message() {
    echo '<p>Hello!</p>';
}
// Missing add_action call here
?>

A The function runs automatically without hooking, so the problem is elsewhere.

B The function name is invalid and causes a fatal error.

C The echo statement is inside a function, so it cannot output anything.

D The function is defined but never hooked to any action, so it never runs.

💡 Hint

Think about how WordPress knows when to run your function.

Defining a function alone does not make WordPress run it. You must hook it to an action with add_action.

❓ state_output

advanced

What is the output order of these hooked functions?

Given these two functions hooked to 'wp_head' with different priorities, what is the order of their output?

Wordpress

<?php
add_action('wp_head', function() { echo 'First'; }, 20);
add_action('wp_head', function() { echo 'Second'; }, 10);
?>

A SecondFirst

B FirstSecond

C They output simultaneously causing an error.

D No output because 'wp_head' is not triggered.

💡 Hint

Lower priority numbers run earlier.

In WordPress, lower priority numbers run first. So the function with priority 10 outputs before priority 20.

🧠 Conceptual

expert

What error occurs if you remove a non-existent action hook?

What happens if you call remove_action('init', 'non_existent_function') in your WordPress code?

Wordpress

remove_action('init', 'non_existent_function');

A No error occurs; WordPress silently ignores it.

B A fatal error occurs because the function does not exist.

C A warning is shown about the missing function.

D The 'init' hook is disabled completely.

💡 Hint

Think about how WordPress handles removing hooks that were never added.

Calling remove_action on a hook-function pair that was never added does nothing and causes no error.