bbPress::instance()

    public static function instance() {

        // Store the instance locally to avoid private static replication
        static $instance = null;

        // Only run these methods if they haven't been ran previously
        if ( null === $instance ) {
            $instance = new bbPress;
            $instance->setup_globals();
            $instance->includes();
            $instance->setup_actions();
        }

        // Always return the instance
        return $instance;
    }