code: public function get($id, $default = NULL) {
  
          $filename = $this->cache_file($id);
  
          if (@filemtime($filename) > time()) {
              $fp = @fopen($filename, 'r');
              if ($fp !== false) {
                  @flock($fp, LOCK_SH);
                  $value = unserialize(@stream_get_contents($fp));
                  @flock($fp, LOCK_UN);
                  @fclose($fp);
                  return $value;
              }
          }
  
          return $default;
      }
docs: Retrieve a cached value entry by id.
  
  @param   string $id id of cache to entry
  @param   string $default default value to return if cache miss
  @return  mixed
  @throws  CacheException