Practice

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1. What is the main purpose of using remove_action or remove_filter in WordPress?

easy

A. To stop a previously added hook from running

B. To add a new hook to WordPress

C. To create a new plugin

D. To update WordPress core files

Solution

Step 1: Understand what hooks do
Hooks let you add or change WordPress features by running custom functions.
Step 2: Purpose of removing hooks
Using remove_action or remove_filter stops those custom functions from running.
Final Answer:
To stop a previously added hook from running -> Option A
Quick Check:
Removing hooks = stopping added functions [OK]

Hint: Removing hooks stops unwanted custom functions [OK]

Common Mistakes:

Thinking remove_action adds hooks
Confusing remove_filter with plugin creation
Assuming remove_action updates WordPress core

2. Which of the following is the correct syntax to remove an action hook named my_custom_action with a callback function my_function?

easy

A. remove_action('my_function', 'my_custom_action');

B. remove_action(my_custom_action, my_function);

C. remove_action('my_custom_action', 'my_function');

D. remove_action('my_custom_action');

Solution

Step 1: Check function parameters
The remove_action function requires the hook name as a string and the callback function name as a string.
Step 2: Match correct order and quotes
remove_action('my_custom_action', 'my_function'); correctly uses quotes and the right order: hook name first, then function name.
Final Answer:
remove_action('my_custom_action', 'my_function'); -> Option C
Quick Check:
Correct syntax = remove_action('hook', 'function') [OK]

Hint: Hook name first, function name second, both in quotes [OK]

Common Mistakes:

Omitting quotes around strings
Swapping hook and function names
Missing the function parameter

3. Given the code below, what will be the output when the page loads?

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

medium

A. Hello!

B. No output

C. PHP error

D. Hello!Hello!

Solution

Step 1: Understand add_action effect
The function greet is added to run on the wp_footer hook, so it would print 'Hello!'.
Step 2: Effect of remove_action
Immediately after adding, remove_action stops greet from running on wp_footer.
Final Answer:
No output -> Option B
Quick Check:
remove_action cancels added hook = no output [OK]

Hint: Remove cancels add, so no output appears [OK]

Common Mistakes:

Assuming add_action still runs after remove_action
Expecting duplicate output
Thinking code causes error

4. What is wrong with this code snippet if the goal is to remove the filter modify_title with callback change_title?

add_filter('the_title', 'change_title', 5);
remove_filter('the_title', 'change_title', 10);

medium

A. Priority missing in add_filter causes remove_filter to fail

B. remove_filter must be called before add_filter

C. Callback function name should be in double quotes

D. Priority must be the same in both add_filter and remove_filter

Solution

Step 1: Check priority in add_filter
The add_filter call uses priority 5.
Step 2: Check priority in remove_filter
The remove_filter specifies priority 10, which does not match.
Step 3: Priority must match
To successfully remove the filter, the priority values must be identical.
Final Answer:
Priority must be the same in both add_filter and remove_filter -> Option D
Quick Check:
Matching priority needed to remove hook [OK]

Hint: Priority must match exactly to remove hooks [OK]

Common Mistakes:

Ignoring priority parameter
Calling remove_filter before add_filter
Using wrong quotes around function name

5. You want to remove a filter added by a plugin, but your remove_filter call does not work. The plugin adds the filter like this:

add_filter('content_filter', ['PluginClass', 'modify_content'], 15);

How should you correctly remove this filter in your theme's functions.php?

hard

A. remove_filter('content_filter', ['PluginClass', 'modify_content'], 15);

B. remove_filter('content_filter', [$this, 'modify_content'], 15);

C. remove_filter('content_filter', [new PluginClass(), 'modify_content'], 15);

D. remove_filter('content_filter', 'modify_content', 15);

Solution

Step 1: Understand how the filter was added
The plugin uses a class method callback: ['PluginClass', 'modify_content'] with priority 15.
Step 2: Remove filter requires the exact same callback
To remove it, you must pass the identical callback array and priority.
Step 3: Use class name and method name array
['PluginClass', 'modify_content'] matches exactly; no object instance needed for class callbacks.
Final Answer:
remove_filter('content_filter', ['PluginClass', 'modify_content'], 15); -> Option A
Quick Check:
Remove class method filter with same array and priority [OK]

Hint: Use same class/method array and priority to remove class callbacks [OK]

Common Mistakes:

Using function name string instead of class method array
Ignoring priority parameter
Passing wrong object or class name

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Keeping heavy hooks active	No direct DOM changes	0	0	[X] Bad
Removing heavy hooks	No direct DOM changes	0	0	[OK] Good

Removing hooks in Wordpress - Performance & Optimization

Practice

Solution

Step 1: Understand what hooks do

Step 2: Purpose of removing hooks

Final Answer:

Quick Check:

Solution

Step 1: Check function parameters

Step 2: Match correct order and quotes

Final Answer:

Quick Check:

Solution

Step 1: Understand add_action effect

Step 2: Effect of remove_action

Final Answer:

Quick Check:

Solution

Step 1: Check priority in add_filter

Step 2: Check priority in remove_filter

Step 3: Priority must match

Final Answer:

Quick Check:

Solution

Step 1: Understand how the filter was added

Step 2: Remove filter requires the exact same callback

Step 3: Use class name and method name array

Final Answer:

Quick Check:

Ready to prove it?