bbp_update_topic_anonymous_reply_count( int $topic_id )

function bbp_update_topic_anonymous_reply_count( $topic_id = 0 ) {
	global $wpdb;

	// If it's a reply, then get the parent (topic id)
	if ( bbp_is_reply( $topic_id ) ) {
		$topic_id = bbp_get_reply_topic_id( $topic_id );
	} elseif ( bbp_is_topic( $topic_id ) ) {
		$topic_id = bbp_get_topic_id( $topic_id );
	} else {
		return;
	}

	$anonymous_replies = (int) $wpdb->get_var( $wpdb->prepare( "SELECT COUNT( ID ) FROM {$wpdb->posts} WHERE ( post_parent = %d AND post_status = '%s' AND post_type = '%s' AND post_author = 0 ) OR ( ID = %d AND post_type = '%s' AND post_author = 0 );", $topic_id, bbp_get_public_status_id(), bbp_get_reply_post_type(), $topic_id, bbp_get_topic_post_type() ) );

	update_post_meta( $topic_id, '_bbp_anonymous_reply_count', (int) $anonymous_replies );

	return apply_filters( 'bbp_update_topic_anonymous_reply_count', (int) $anonymous_replies, $topic_id );
}