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 in AGENTS.md)

Available Integrations

• BuddyPress

• bbPress

• WooCommerce

• Jetpack

• The Events Calendar

• WP User Avatars

• And 13+ more

For complete directory structure and naming conventions, see docs/php-class-structure.md .

Creating New Integration

Basic Integration Class

<?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

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

Custom Transformers

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

\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

// 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

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

Hook Priority

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

Namespace Conflicts

// 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