code: public function set($key, \DateTime $time)
      {
          $time = $time->getTimestamp();
          $file = $this->getFilename($key);
          if (!file_exists($file) || $time > filemtime($file)) {
              return touch($file, $time);
          }
  
          return true;
      }
docs: @param string $key
  @param \DateTime $time
  
  @return bool