bbp_is_user_favorite( int $user_id, int $topic_id )

function bbp_is_user_favorite( $user_id = 0, $topic_id = 0 ) {

	$user_id = bbp_get_user_id( $user_id, true, true );
	if ( empty( $user_id ) )
		return false;

	$retval    = false;
	$favorites = bbp_get_user_favorites_topic_ids( $user_id );

	if ( !empty( $favorites ) ) {

		// Checking a specific topic id
		if ( !empty( $topic_id ) ) {
			$topic    = bbp_get_topic( $topic_id );
			$topic_id = !empty( $topic ) ? $topic->ID : 0;

		// Using the global topic id
		} elseif ( bbp_get_topic_id() ) {
			$topic_id = bbp_get_topic_id();

		// Use the current post id
		} elseif ( !bbp_get_topic_id() ) {
			$topic_id = get_the_ID();
		}

		// Is topic_id in the user's favorites
		if ( !empty( $topic_id ) ) {
			$retval = in_array( $topic_id, $favorites );
		}
	}

	return (bool) apply_filters( 'bbp_is_user_favorite', (bool) $retval, $user_id, $topic_id, $favorites );
}