code: public function has($key)
      {
          $conf =& $this->conf;
          $keys = explode('.', $key);
  
          foreach ($keys as $test) {
              $direct = implode('.', $keys);
  
              // Check for a direct match, containing dot
              if (is_array($conf) && array_key_exists($direct, $conf)) {
                  return true;
              }
  
              if (!is_array($conf) || !array_key_exists($test, $conf)) {
                  return false;
              }
  
              $conf =& $conf[$test];
              array_shift($keys);
          }
  
          return true;
      }
docs: {@inheritdoc}