code: public function setApcuPrefix($apcuPrefix)
      {
          $this->apcuPrefix = function_exists('apcu_fetch') && filter_var(ini_get('apc.enabled'), FILTER_VALIDATE_BOOLEAN) ? $apcuPrefix : null;
      }
docs: APCu prefix to use to cache found/not-found classes, if the extension is enabled.
  
  @param string|null $apcuPrefix