code: public static function getCache($name)
      {
          $cache_file = self::getCacheName($name);
          if (file_exists($cache_file) && ($content = file_get_contents($cache_file))) {
              $data = unserialize($content);
              if (isset($data['expired']) && (intval($data['expired']) === 0 || intval($data['expired']) >= time())) {
                  return $data['value'];
              }
              self::delCache($name);
          }
          return null;
      }
docs: 获取缓存内容
  @param string $name 缓存名称
  @return null|mixed