ActivityPub Integrations

This skill provides guidance on integrating the ActivityPub plugin with other WordPress plugins.

Quick Reference

Integration Location

All integrations live in the integration/ directory.

File naming: class-{plugin-name}.php (following PHP conventions)

Available Integrations

BuddyPress
bbPress
WooCommerce
Jetpack
The Events Calendar
WP User Avatars
And 13+ more

For complete directory structure and naming conventions, see PHP Class Structure.

Creating New Integration

Basic Integration Class

php

<?php
namespace Activitypub\Integration;

class Plugin_Name {
    public static function init() {
        \add_filter( 'activitypub_transformer', array( self::class, 'custom_transformer' ), 10, 2 );
        \add_filter( 'activitypub_post_types', array( self::class, 'add_post_types' ) );
    }

    public static function custom_transformer( $transformer, $object ) {
        // Return custom transformer if needed.
        return $transformer;
    }

    public static function add_post_types( $post_types ) {
        // Add plugin's post types.
        $post_types[] = 'plugin_post_type';
        return $post_types;
    }
}

Integration Patterns

Adding Post Type Support

php

public static function add_post_types( $post_types ) {
    $post_types[] = 'event';
    $post_types[] = 'product';
    return $post_types;
}

Custom Transformers

php

public static function transformer( $transformer, $object ) {
    if ( 'custom_type' === get_post_type( $object ) ) {
        require_once __DIR__ . '/transformer/class-custom.php';
        return new Transformer\Custom( $object );
    }
    return $transformer;
}

Modifying Activities

php

\add_filter( 'activitypub_activity_object', function( $object, $post ) {
    if ( 'product' === get_post_type( $post ) ) {
        $object['type']  = 'Product';
        $object['price'] = get_post_meta( $post->ID, 'price', true );
    }
    return $object;
}, 10, 2 );

Testing Integrations

Verify Integration Loading

php

// Check if integration is active.
if ( class_exists( '\Activitypub\Integration\Plugin_Name' ) ) {
    // Integration loaded.
}

Test Compatibility

Install target plugin
Activate ActivityPub
Check for conflicts
Verify custom post types work
Test federation of plugin content

Common Integration Issues

Plugin Detection

php

// Multiple detection methods.
if ( defined( 'PLUGIN_VERSION' ) ) { }
if ( function_exists( 'plugin_function' ) ) { }
if ( class_exists( 'Plugin_Class' ) ) { }

Hook Priority

php

// Use appropriate priority.
add_filter( 'hook', 'callback', 20 ); // After plugin's filter.

Namespace Conflicts

php

// Use fully qualified names.
$object = new \Plugin\Namespace\Class();

Existing Integrations

BuddyPress

Adds BuddyPress activity support
Custom member transformers
Group activity federation

WooCommerce

Product post type support
Order activity notifications
Customer review federation

bbPress

Forum topic federation
Reply activities
User forum profiles

Best Practices

Always check if plugin is active before adding hooks
Use late priority for filters to override plugin defaults
Test with multiple plugin versions
Document compatibility requirements
Handle plugin deactivation gracefully

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