ICT:Hooks – How Hooks Work in MediaWiki

This page explains how MediaWiki’s hook system works, where hook parameters such as $skin, $bar, and $links come from, and how administrators can look up the official documentation for each hook.

This page is intended for future stewards of the archive infrastructure.

1. What a Hook Is

A hook is a point inside MediaWiki’s execution flow where custom PHP code can run.

MediaWiki internally calls:

Hooks::run( 'HookName', [ $param1, $param2, ... ] );

Your code registers a function to be executed at that moment:

$wgHooks['HookName'][] = function ( $param1, $param2 ) {
    # custom logic
    return true;
};

Returning true tells MediaWiki to continue normal processing. Returning false stops further handlers.

2. Where Do Parameters Like `$skin`, `$bar`, `$links` Come From

Each hook defines:

how many parameters it passes
what type each parameter is
whether parameters are passed by reference
what you are allowed to modify

This information is published in the official MediaWiki hook documentation.

For example:

SkinBuildSidebar

Documentation: https://www.mediawiki.org/wiki/Manual:Hooks/SkinBuildSidebar
Parameters:

 * $skin — instance of Skin or a subclass (e.g., SkinVector)
 * &$bar — associative array representing the sidebar sections

SkinTemplateNavigation::Universal

Documentation: https://www.mediawiki.org/wiki/Manual:Hooks/SkinTemplateNavigation::Universal
Parameters:

 * $skin — instance of SkinTemplate
 * &$links — nested array containing the action tabs (views, actions, variants)

These pages define exactly what the objects contain and how they may be modified.

3. How to Read Hook Documentation

Every hook page on mediawiki.org includes:

a description of when the hook fires
a list of parameters
the PHP types of each parameter
examples of usage
notes about return values

Example from the documentation:

/**
 * @param Skin $skin
 * @param array &$bar
 */

This tells you:

$skin is a Skin object
$bar is an array passed by reference
modifying $bar changes the sidebar

4. Why Hooks Are Used in LocalSettings.php

Hooks allow you to:

hide or modify UI elements
enforce role‑based behavior
override default navigation
add or remove actions
customize rendering without modifying core files

They are the official, stable way to extend MediaWiki.

All hook code in LocalSettings.php is standard PHP.

5. Example: Understanding the Parameters

Example 1: SkinBuildSidebar

function ( $skin, &$bar ) { ... }

$skin → gives access to:

 * $skin->getUser()
 * $skin->getTitle()
 * $skin->getSkinName()

$bar → the sidebar structure:

$bar = [
    'navigation' => [
        [ 'text' => 'Main Page', 'href' => '/wiki/Main_Page' ],
    ],
    'tools' => [ ... ],
];

Example 2: SkinTemplateNavigation::Universal

function ( $skin, &$links ) { ... }

$links contains the action tabs:

$links = [
    'views' => [
        'edit' => [ 'text' => 'Edit', 'href' => ... ],
        'history' => [ ... ],
    ],
    'actions' => [
        'delete' => [ ... ],
        'move' => [ ... ],
    ],
];

6. How to Find Any Hook

All hooks are listed here:

https://www.mediawiki.org/wiki/Manual:Hooks

Each hook page includes:

purpose
parameters
examples
version notes

This is the authoritative reference for understanding hook parameters.

7. Why This Matters for Successors

Understanding hooks ensures that future stewards can:

safely modify UI behavior
understand why certain elements are hidden
maintain or extend the decluttered interface
avoid modifying core files or skins
keep the system stable and upgrade‑friendly

This page provides the conceptual foundation needed to understand the hook‑based customizations used in the archive infrastructure.

This page is part of the ICT documentation set for the archive infrastructure.