bbp_update_topic_reply_count_hidden( int $topic_id, int $reply_count )

function bbp_update_topic_reply_count_hidden( $topic_id = 0, $reply_count = 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 );
	} else {
		$topic_id = bbp_get_topic_id( $topic_id );
	}

	// Get replies of topic
	if ( empty( $reply_count ) ) {
		$post_status = "'" . implode( "','", array( bbp_get_trash_status_id(), bbp_get_spam_status_id() ) ) . "'";
		$reply_count = $wpdb->get_var( $wpdb->prepare( "SELECT COUNT(ID) FROM {$wpdb->posts} WHERE post_parent = %d AND post_status IN ( {$post_status} ) AND post_type = '%s';", $topic_id, bbp_get_reply_post_type() ) );
	}

	update_post_meta( $topic_id, '_bbp_reply_count_hidden', (int) $reply_count );

	return apply_filters( 'bbp_update_topic_reply_count_hidden', (int) $reply_count, $topic_id );
}