public static function bulkEnqueue($handlers, $queue = "default", $run_at = null) {
        $sql = "INSERT INTO " . self::$jobsTable . " (handler, queue, run_at, created_at) VALUES";
        $sql .= implode(",", array_fill(0, count($handlers), "(?, ?, ?, NOW())"));

        $parameters = array();
        foreach ($handlers as $handler) {
            $parameters []= serialize($handler);
            $parameters []= (string) $queue;
            $parameters []= $run_at;
        }
        $affected = self::runUpdate($sql, $parameters);

        if ($affected < 1) {
            self::log("[JOB] failed to enqueue new jobs", self::ERROR);
            return false;
        }

        if ($affected != count($handlers))
            self::log("[JOB] failed to enqueue some new jobs", self::ERROR);

        return true;
    }