private function clearLog($flags)
    {
        $return = null;
        $clearErrors = $flags & Debug::CLEAR_LOG_ERRORS;
        if ($flags & Debug::CLEAR_LOG) {
            $return = 'log ('.($clearErrors ? 'incl errors' : 'sans errors').')';
            $curDepth = 0;
            foreach ($this->data['groupStacks']['main'] as $group) {
                $curDepth += (int) $group['collect'];
            }
            $entriesKeep = $this->debug->internal->getCurrentGroups($this->data['log'], $curDepth);
            $this->clearLogHelper($this->data['log'], $clearErrors, $entriesKeep);
        } elseif ($clearErrors) {
            $return = 'errors';
        }
        return $return;
    }