function groups_notification_group_updated( $group_id = 0, $old_group = null ) {
	$group = groups_get_group( $group_id );

	if ( $old_group instanceof BP_Groups_Group ) {
		$changed = array();

		if ( $group->name !== $old_group->name ) {
			$changed[] = sprintf(
				_x( '* Name changed from "%s" to "%s".', 'Group update email text', 'buddypress' ),
				esc_html( $old_group->name ),
				esc_html( $group->name )
			);
		}

		if ( $group->description !== $old_group->description ) {
			$changed[] = sprintf(
				_x( '* Description changed from "%s" to "%s".', 'Group update email text', 'buddypress' ),
				esc_html( $old_group->description ),
				esc_html( $group->description )
			);
		}

		if ( $group->slug !== $old_group->slug ) {
			$changed[] = sprintf(
				_x( '* Permalink changed from "%s" to "%s".', 'Group update email text', 'buddypress' ),
				esc_url( bp_get_group_permalink( $old_group ) ),
				esc_url( bp_get_group_permalink( $group ) )
			);
		}
	}

	/**
	 * Filters the bullet points listing updated items in the email notification after a group is updated.
	 *
	 * @since 2.2.0
	 *
	 * @param array $changed Array of bullet points.
	 */
	$changed = apply_filters( 'groups_notification_group_update_updated_items', $changed );

	$changed_text = '';
	if ( ! empty( $changed ) ) {
		$changed_text = implode( "\n", $changed );
	}

	$user_ids = BP_Groups_Member::get_group_member_ids( $group->id );
	foreach ( (array) $user_ids as $user_id ) {

		// Continue if member opted out of receiving this email.
		if ( 'no' === bp_get_user_meta( $user_id, 'notification_groups_group_updated', true ) ) {
			continue;
		}

		$unsubscribe_args = array(
			'user_id'           => $user_id,
			'notification_type' => 'groups-details-updated',
		);

		$args = array(
			'tokens' => array(
				'changed_text' => $changed_text,
				'group'        => $group,
				'group.id'     => $group_id,
				'group.url'    => esc_url( bp_get_group_permalink( $group ) ),
				'group.name'   => $group->name,
				'unsubscribe'  => esc_url( bp_email_get_unsubscribe_link( $unsubscribe_args ) ),
			),
		);
		bp_send_email( 'groups-details-updated', (int) $user_id, $args );
	}

	/**
	 * Fires after the notification is sent that a group has been updated.
	 *
	 * See https://buddypress.trac.wordpress.org/ticket/3644 for blank message parameter.
	 *
	 * @since 1.5.0
	 * @since 2.5.0 $subject has been unset and is deprecated.
	 *
	 * @param array  $user_ids Array of user IDs to notify about the update.
	 * @param string $subject  Deprecated in 2.5; now an empty string.
	 * @param string $value    Empty string preventing PHP error.
	 * @param int    $group_id ID of the group that was updated.
	 */
	do_action( 'bp_groups_sent_updated_email', $user_ids, '', '', $group_id );
}