public function export()
    {
        // 获取导出数量
        $count = (int)$this->input->get('export_count');
        if ($count <= 0) {
            dr_json(0, '请输入有效的导出数量');
        }
        // 查询最后的 $count 条记录
        $table = SITE_ID . '_app_kami';
        $kamis = $this->model->table($table)
                             ->order_by('id', 'desc')
                             ->limit($count)
                             ->get_all();
        if (empty($kamis)) {
            dr_json(0, '没有找到足够的卡密数据');
        }
        // 将卡密写入TXT文件
        $filename = '卡密列表_' . date('YmdHis') . '.txt';
        $fp = fopen($filename, 'w');
    
        foreach ($kamis as $kami) {
            fwrite($fp, $kami['kami'] . "\n");
        }
        fclose($fp);
        // 提供下载
        header('Content-Type: text/plain');
        header("Content-Disposition: attachment; filename=\"" . basename($filename) . "\"");
        readfile($filename);
        unlink($filename); // 删除临时文件
        exit;
    }