Action hooks in Wordpress - Step-by-Step Execution

Concept Flow - Action hooks

WordPress loads core

↓

Action hook triggered

↓

Check for functions hooked

↓

No hooked functions

↓

Continue normal flow

↓

Continue normal flow

WordPress runs its core, triggers an action hook, then runs all functions attached to that hook before continuing.

Execution Sample

Wordpress

<?php
add_action('init', 'say_hello');
function say_hello() {
  echo 'Hello!';
}
?>

This code attaches a function to the 'init' action hook that prints 'Hello!' when WordPress initializes.

Execution Table

Step	Action Hook Triggered	Hooked Functions Found	Function Executed	Output
1	init	say_hello	say_hello()	Hello!
2	wp_footer	none	none
3	shutdown	none	none

💡 No more hooks triggered, WordPress finishes loading.

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
hook	none	init	wp_footer	shutdown
functions_hooked	none	['say_hello']	[]	[]
output	""	"Hello!"	"Hello!"	"Hello!"

Key Moments - 2 Insights

Why does 'say_hello' run only when the 'init' hook triggers?

Because in the execution_table at Step 1, the 'init' hook triggers and WordPress finds 'say_hello' hooked to it, so it runs. Other hooks have no functions hooked.

What happens if no functions are hooked to an action?

As shown in Steps 2 and 3 in the execution_table, WordPress triggers the hook but finds no functions, so it continues without output or changes.

Visual Quiz - 3 Questions

Look at the execution_table, what is the output after the 'init' hook runs?

A "Hello!"

B "Goodbye!"

C "" (empty)

D "Init hook triggered"

💡 Hint

Check Step 1 in the execution_table under Output column.

At which step does WordPress find no hooked functions?

A Step 1

B Step 2

C Both Step 2 and Step 3

D Step 3

💡 Hint

Look at Hooked Functions Found column in the execution_table.

If we add a function hooked to 'wp_footer', what changes in the execution_table?

A Step 1 output changes

B Step 2 will show the function executed and output updated

C Step 3 will show the function executed

D No changes at all

💡 Hint

Adding a hooked function affects the step where that hook triggers, see Step 2 in execution_table.

Concept Snapshot

Action hooks let you run your code at specific points in WordPress.
Use add_action('hook_name', 'your_function') to attach your function.
When WordPress triggers that hook, your function runs.
If no functions are hooked, WordPress continues normally.
Hooks help customize behavior without changing core files.

Full Transcript

Action hooks in WordPress are points where the system pauses and runs any functions you have attached. When WordPress loads, it triggers hooks like 'init' or 'wp_footer'. If you have used add_action to attach a function to a hook, WordPress runs that function at that moment. For example, attaching 'say_hello' to 'init' makes WordPress print 'Hello!' when it initializes. If no functions are attached to a hook, WordPress just continues without changes. This lets you add or change behavior safely and cleanly.