code: protected function getValues($keys)
      {
          $values = $this->useApcu ? apcu_fetch($keys) : apc_fetch($keys);
          return is_array($values) ? $values : [];
      }
docs: Retrieves multiple values from cache with the specified keys.
  @param array $keys a list of keys identifying the cached values
  @return array a list of cached values indexed by the keys