code: protected function buildChannelTree()
      {
          if ($this->channels == array($this->channelNameRoot)) {
              return array();
          }
          \sort($this->channels);
          // move root to the top
          $rootKey = \array_search($this->channelNameRoot, $this->channels);
          if ($rootKey !== false) {
              unset($this->channels[$rootKey]);
              \array_unshift($this->channels, $this->channelName);
          }
          $tree = array();
          foreach ($this->channels as $channel) {
              $ref = &$tree;
              $path = \explode('.', $channel);
              foreach ($path as $k) {
                  if (!isset($ref[$k])) {
                      $ref[$k] = array();
                  }
                  $ref = &$ref[$k];
              }
          }
          return $tree;
      }
docs: Build a tree of all channels that have been output
  
  @return array