bbp_notify_topic_subscribers( int $reply_id, int $topic_id, int $forum_id, mixed $anonymous_data = false, int $reply_author )

function bbp_notify_topic_subscribers( $reply_id = 0, $topic_id = 0, $forum_id = 0, $anonymous_data = false, $reply_author = 0 ) {

	// Bail if subscriptions are turned off
	if ( !bbp_is_subscriptions_active() ) {
		return false;
	}

	/** Validation ************************************************************/

	$reply_id = bbp_get_reply_id( $reply_id );
	$topic_id = bbp_get_topic_id( $topic_id );
	$forum_id = bbp_get_forum_id( $forum_id );

	/** Topic *****************************************************************/

	// Bail if topic is not published
	if ( !bbp_is_topic_published( $topic_id ) ) {
		return false;
	}

	/** Reply *****************************************************************/

	// Bail if reply is not published
	if ( !bbp_is_reply_published( $reply_id ) ) {
		return false;
	}

	// Poster name
	$reply_author_name = bbp_get_reply_author_display_name( $reply_id );

	/** Mail ******************************************************************/

	// Remove filters from reply content and topic title to prevent content
	// from being encoded with HTML entities, wrapped in paragraph tags, etc...
	remove_all_filters( 'bbp_get_reply_content' );
	remove_all_filters( 'bbp_get_topic_title'   );

	// Strip tags from text and setup mail data
	$topic_title   = strip_tags( bbp_get_topic_title( $topic_id ) );
	$topic_url     = get_permalink( $topic_id );
	$reply_content = strip_tags( bbp_get_reply_content( $reply_id ) );
	$reply_url     = bbp_get_reply_url( $reply_id );

	$forum_title   = wp_strip_all_tags( get_post_field( 'post_title', $forum_id ) );
	$forum_url     = esc_url( bbp_get_forum_permalink( $forum_id ) );

	$args = array(
		'tokens' => array(
			'forum.title'      => $forum_title,
			'forum.url'        => $forum_url,
			'discussion.title' => $topic_title,
			'discussion.url'   => $topic_url,
			'reply.id'         => $reply_id,
			'reply.url'        => $reply_url,
			'reply.content'    => $reply_content,
			'poster.name'      => $reply_author_name,
		),
	);

	// Get topic subscribers and bail if empty
	$user_ids = bbp_get_topic_subscribers( $topic_id, true );

	// Dedicated filter to manipulate user ID's to send emails to
	$user_ids = apply_filters( 'bbp_topic_subscription_user_ids', $user_ids );
	if ( empty( $user_ids ) ) {
		return false;
	}

	/** Send it ***************************************************************/

	do_action( 'bbp_pre_notify_subscribers', $reply_id, $topic_id, $user_ids );

	// Loop through users
	foreach ( (array) $user_ids as $user_id ) {

		// Don't send notifications to the person who made the post
		if ( !empty( $reply_author ) && (int) $user_id === (int) $reply_author ) {
			continue;
		}

		// Send notification email.
		bp_send_email( 'bbp-new-forum-reply', (int) $user_id, $args );
	}

	do_action( 'bbp_post_notify_subscribers', $reply_id, $topic_id, $user_ids );

	return true;
}