Source Reference:

• Component: bbPress :: bbp-forum

  File: /bbp-includes/bbp-forum-template.php :: Trac Source Line: 192

  		// Currently viewing a topic
  		elseif ( bbp_is_single_topic() )
  			$bbp_forum_id = $bbp->current_forum_id = bbp_get_topic_forum_id();
  
  		// Fallback
  		else
  			$bbp_forum_id = 0;
  
  		return apply_filters( 'bbp_get_forum_id', (int) $bbp_forum_id, $forum_id );
  	}
  
  /**
   * Gets a forum
   *
   * @since bbPress (r2787)
   *
   * @param int|object $forum forum id or forum object
   * @param string $output Optional. OBJECT, ARRAY_A, or ARRAY_N. Default = OBJECT
   * @param string $filter Optional Sanitation filter. See {@link sanitize_post()}