Common filter hooks in Wordpress - Step-by-Step Execution

Concept Flow - Common filter hooks

WordPress loads

↓

Apply filter hook

↓

Call all hooked functions

↓

Each function modifies data

↓

Return modified data

↓

Continue with filtered data

WordPress runs filter hooks by calling all functions attached to a hook, each can change the data before it is used.

Execution Sample

Wordpress

<?php
add_filter('the_title', 'add_prefix_to_title');
function add_prefix_to_title($title) {
  return 'Prefix: ' . $title;
}
?>

This code adds a prefix to post titles using the 'the_title' filter hook.

Execution Table

Step	Hook Triggered	Data Before	Function Called	Data After	Next Action
1	'the_title'	'Hello World'	add_prefix_to_title	'Prefix: Hello World'	Return modified title
2	End of filter functions	'Prefix: Hello World'	None	'Prefix: Hello World'	Use filtered title in page

💡 All hooked functions executed; filtered data returned for use.

Variable Tracker

Variable	Start	After add_prefix_to_title	Final
$title	'Hello World'	'Prefix: Hello World'	'Prefix: Hello World'

Key Moments - 2 Insights

Why does the title change after the filter runs?

Because the function 'add_prefix_to_title' modifies the title and returns the new value, as shown in step 1 of the execution_table.

What happens if multiple functions are hooked to the same filter?

Each function runs in order, receiving the data modified by the previous function, so the data changes step by step before final use.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of data after 'add_prefix_to_title' runs?

A 'Hello World'

B 'Hello World Prefix:'

C 'Prefix: Hello World'

D 'Prefix Hello World'

💡 Hint

Check the 'Data After' column in step 1 of the execution_table.

At which step does WordPress stop calling filter functions?

A Step 1

B Step 2

C Step 3

D Step 0

💡 Hint

Look for the row where 'Function Called' is 'None' in the execution_table.

If you add another function hooked to 'the_title' that adds '!!!' at the end, how would the data change after step 1?

A 'Prefix: Hello World!!!'

B 'Prefix: Hello World'

C 'Hello World!!!'

D '!!! Prefix: Hello World'

💡 Hint

Remember each hooked function modifies the data passed from the previous one.

Concept Snapshot

Common filter hooks let you change data in WordPress.
Use add_filter('hook_name', 'your_function') to attach.
Your function gets data, modifies it, returns it.
WordPress runs all hooked functions in order.
Final modified data is used in the site.

Full Transcript

In WordPress, common filter hooks let you change data before it is used. When WordPress runs a filter hook, it calls all functions attached to that hook. Each function receives the current data, changes it if needed, and returns it. The next function gets the modified data. After all functions run, WordPress uses the final data. For example, the 'the_title' filter lets you change post titles. You add a function with add_filter('the_title', 'your_function'). Your function takes the title, adds a prefix, and returns it. WordPress then shows the modified title on the page. This process helps customize WordPress behavior without changing core code.