Hooks and Events

Overview

XOOPS provides hooks and events as extension points that allow modules to interact with core functionality and each other without direct dependencies.

Hooks vs Events

Aspect	Hooks	Events
Purpose	Modify behavior/data	React to occurrences
Return	Can return modified data	Typically void
Timing	Before/during action	After action
Pattern	Filter chain	Observer/pub-sub

Hook System

Registering Hooks

// Register a hook in xoops_version.php
$modversion['hooks'][] = [
    'name'     => 'user.profile.display',
    'callback' => 'mymodule_hook_user_profile',
    'priority' => 10,
];

Hook Callback

include/hooks.php

function mymodule_hook_user_profile(array $data): array
{
    $userId = $data['user_id'];

    // Add custom profile fields
    $data['fields']['reputation'] = mymodule_get_user_reputation($userId);
    $data['fields']['badges'] = mymodule_get_user_badges($userId);

    return $data;
}

Available Core Hooks

Hook Name	Data	Description
user.profile.display	User data array	Modify profile display
content.render	Content HTML	Filter content output
form.submit	Form data	Validate/modify form data
search.results	Results array	Filter search results
menu.main	Menu items	Modify main menu

Event System

Dispatching Events

// In your module code
$eventHandler = xoops_getHandler('event');

$eventHandler->trigger('mymodule.article.created', [
    'article_id' => $article->id(),
    'author_id'  => $article->authorId(),
    'title'      => $article->title(),
]);

Listening for Events

class/Preload.php

class MyModulePreload extends \Xmf\Module\Helper\AbstractHelper
{
    public function eventMymoduleArticleCreated(array $args): void
    {
        $articleId = $args['article_id'];

        // Notify subscribers
        $this->notifyNewArticle($articleId);
    }

    public function eventUserLogin(array $args): void
    {
        $userId = $args['userid'];

        // Update last login for module
        $this->updateUserActivity($userId);
    }
}

Preload Events Reference

Core Events

// Header/Footer
public function eventCoreHeaderStart(array $args): void {}
public function eventCoreHeaderEnd(array $args): void {}
public function eventCoreFooterStart(array $args): void {}
public function eventCoreFooterEnd(array $args): void {}

// Includes
public function eventCoreIncludeCommonStart(array $args): void {}
public function eventCoreIncludeCommonEnd(array $args): void {}

// Exceptions
public function eventCoreException(array $args): void {}

User Events

public function eventUserLogin(array $args): void {}
public function eventUserLogout(array $args): void {}
public function eventUserRegister(array $args): void {}
public function eventUserActivate(array $args): void {}
public function eventUserDelete(array $args): void {}

Module Events

public function eventSystemModuleInstall(array $args): void {}
public function eventSystemModuleUninstall(array $args): void {}
public function eventSystemModuleUpdate(array $args): void {}
public function eventSystemModuleActivate(array $args): void {}
public function eventSystemModuleDeactivate(array $args): void {}

Custom Module Events

Defining Events

// Define event constants
class ArticleEvents
{
    public const CREATED = 'mymodule.article.created';
    public const UPDATED = 'mymodule.article.updated';
    public const DELETED = 'mymodule.article.deleted';
    public const PUBLISHED = 'mymodule.article.published';
}

Triggering Events

class ArticleService
{
    public function publish(Article $article): void
    {
        $article->publish();
        $this->repository->save($article);

        // Trigger event
        $GLOBALS['xoopsPreload']->triggerEvent(
            ArticleEvents::PUBLISHED,
            ['article' => $article]
        );
    }
}

Listening to Module Events

// In another module's Preload.php

public function eventMymoduleArticlePublished(array $args): void
{
    $article = $args['article'];

    // Index for search
    $this->searchIndexer->index($article);

    // Update sitemap
    $this->sitemapGenerator->addUrl($article->url());
}

Best Practices

1. Use Specific Names - module.entity.action format
2. Pass Minimal Data - Only what listeners need
3. Document Events - List events in module docs
4. Avoid Side Effects - Keep listeners focused
5. Handle Errors - Don’t let listener errors break flow

Related Documentation

• Event-System - Detailed event documentation
• ../03-Module-Development/Module-Development - Module development
• ../07-XOOPS-4.0/Implementation-Guides/Event-System-Guide - PSR-14 events