一、因为项目中的一个报表需要合并三个表的数据，所以分表查询再合并数据，利用PHP数组函数进行排序，搜索。三表合并后的数组结构如下：

Array
(
    [0] => Array
        (
            [history_id] => 12
            [sla_group_id] => 1
            [sla_id] => -1
            [create_time] => 1513057695
            [tasklog_id] => 12
            [tasklog_time] => 2017-12-12 13:48:15
            [tasklog_name] => window_2008
            [tasklog_type] => 分组立即调度
            [tasklog_user] => admin
            [tasklog_status] => 3
        )

    [1] => Array
        (
            [history_id] => 11
            [sla_group_id] => 1
            [sla_id] => 1
            [create_time] => 1513057563
            [tasklog_id] => 11
            [tasklog_time] => 2017-12-12 13:46:03
            [tasklog_name] => centos7_USHARK
            [tasklog_type] => 一小时备份频率
            [tasklog_user] => 系统自动
            [tasklog_status] => 3
        )

    [2] => Array
        (
            [history_id] => 19
            [sla_group_id] => 1
            [sla_id] => 98
            [create_time] => 1513059714
            [tasklog_id] => 19
            [tasklog_time] => 2017-12-12 14:21:54
            [tasklog_name] => huawei_fusion_backup
            [tasklog_type] => 华为虚拟化备份
            [tasklog_user] => ushark.net
            [tasklog_status] => 2
        )

    [3] => Array
        (
            [history_id] => 41
            [sla_group_id] => 0
            [sla_id] => -1
            [create_time] => 1513069534
            [status] => 2
            [tasklog_id] => 41
            [tasklog_time] => 2017-12-12 17:05:34
            [tasklog_name] => centos7-11自增非整数测试
            [tasklog_user] => admin
            [tasklog_type] => 立即调度
            [tasklog_status] => 2
        )

    [4] => Array
        (
            [history_id] => 40
            [sla_group_id] => 0
            [sla_id] => -1
            [create_time] => 1513067574
            [status] => 2
            [tasklog_id] => 40
            [tasklog_time] => 2017-12-12 16:32:54
            [tasklog_name] => win2008安装MySQL
            [tasklog_user] => impp.cc
            [tasklog_type] => 策略备份
            [tasklog_status] => 2
        )

    [5] => Array
        (
            [history_id] => 39
            [sla_group_id] => 0
            [sla_id] => -1
            [create_time] => 1513067399
            [status] => 2
            [tasklog_id] => 39
            [tasklog_time] => 2017-12-12 16:29:59
            [tasklog_name] => Linux下文件
            [tasklog_user] => ppstorm.com
            [tasklog_type] => 立即调度
            [tasklog_status] => 2
        )
)

二、二维数组排序、搜索

// HTTP GET values
$length  = (int) $this->input->get('length', true);
$start   = (int) $this->input->get('start', true);
$order   = trim($this->input->get('order', true));
$sort    = trim($this->input->get('dir', true));
$search  = trim($this->input->get('search', true));

// 三表数据
$vm_group = $this->safe->vm_group_task();
$vm_tasklog = $this->safe->vm_tasklog();
$vm_mounts_log = $this->safe->vm_mounts_log();

// 合并数据
$tasklog = array_merge($vm_group, $vm_tasklog, $vm_mounts_log);

// !!! 二维数据搜索 !!!
if (!empty($search)) {
    foreach ($tasklog as $sk => $sv) {
        if (mb_stripos($sv['tasklog_name'], $search) === false
            && mb_stripos($sv['tasklog_type'], $search) === false
            && mb_stripos($sv['tasklog_user'], $search) === false
        ) {
            unset($tasklog[$sk]);
            continue;
        }
    }
}

// 总记录
$total_record = count($tasklog);

// 排序
switch ($order) {
    case 1:
        $sort_key = 'tasklog_name';
        break;
    case 2:
        $sort_key = 'tasklog_type';
        break;
    case 3:
        $sort_key = 'tasklog_user';
        break;
    case 4:
        $sort_key = 'tasklog_time';
        break;
    case 5:
        $sort_key = 'tasklog_status';
        break;
    default:
        $sort_key = 'tasklog_id';
        break;
}
$sort_arr = array_column($tasklog, $sort_key);
$desc_asc = $sort === 'desc' ? SORT_DESC : SORT_ASC;
array_multisort($sort_arr, $desc_asc, $tasklog); // !!! 二维数据排序 !!!

// 取指定长度
$output_arr = array_slice($tasklog, $start, $length);