code: protected function setValues($data, $duration)
      {
          $result = $this->useApcu ? apcu_store($data, null, $duration) : apc_store($data, null, $duration);
          return is_array($result) ? array_keys($result) : [];
      }
docs: Stores multiple key-value pairs in cache.
  @param array $data array where key corresponds to cache key while value
  @param int $duration the number of seconds in which the cached values will expire. 0 means never expire.
  @return array array of failed keys