datatable表格框架服务器端分页查询设置

js代码如下：
$('#mytable').dataTable(
        {
            "bServerSide": true, //开启服务器模式，使用服务器端处理配置datatable。注意：sAjaxSource参数也必须被给予为了给datatable源代码来获取所需的数据对于每个画。 这个翻译有点别扭。开启此模式后，你对datatables的每个操作 每页显示多少条记录、下一页、上一页、排序（表头）、搜索，这些都会传给服务器相应的值。
            "sAjaxSource": "ajax.php", //给服务器发请求的url
            "aoColumns": [ //这个属性下的设置会应用到所有列，按顺序，没有是空
                {"sDefaultContent": ''},//checkbox column 相当于占位符，等待填充。也可以指定值如 {"mData": 'ip'}
                {"sDefaultContent": ''},//ip column
                {"sDefaultContent": ''},//nip column
                {"sDefaultContent": ''},//role column
                {"sDefaultContent": ''},//gamenserver column
                {"sDefaultContent": ''},//serverid column
                {"sDefaultContent": ''},//status column
                {"sDefaultContent": ''},//remark column
                {"sDefaultContent": ''},//ctime column
                {"sDefaultContent": '', "sClass": "action"},//sClass 表示给本列加class
            ],
            "aoColumnDefs": [//和aoColums类似，但他可以给指定列赋予属性
                {"bSortable": false, "aTargets": [0,7,9]},  //这句话意思是第7,9列（从0开始算）不排序

            ],
            "aaSorting": [[1, "asc"]], //默认排序

            "fnRowCallback": function(nRow, aData, iDisplayIndex) {// 给各列填充内容
                $('td:eq(0)', nRow).html('<label><input type="checkbox" id="hids[]" value="'+aData.id+'-'+aData.status+'" name="hids[]"></label>');

                $('td:eq(2)', nRow).html(aData.nip);

                var role = aData.role.split(' ');
                var href = "";
                for(var i=0;i<role.length;i++){
                    href += '<a href="host.php?ser='+role[i]+'">'+role[i]+'</a> ';
                }
                $('td:eq(3)', nRow).html(href);

                $('td:eq(4)', nRow).html(aData.gameserver);
                $('td:eq(5)', nRow).html(aData.serverid);
                $('td:eq(7)', nRow).html(aData.remark);
                $('td:eq(8)', nRow).html(aData.ctime);

                if (aData.status == 1) {
                    if(aData.hostscreenid){
                        $('td:eq(1)', nRow).html('<a href="http://11.111.111.11:8081/screen/'+aData.hostscreenid+'"><span style="color:red;">'+aData.ip+'</span></a>');
                    }else{
                        $('td:eq(1)', nRow).html("<span style='color:red;'>"+aData.ip+"</span>");
                    }
                    $('td:eq(6)', nRow).html("<span style='color:red;'>线下</span>");
                } else if (aData.status == 0) {
                    if(aData.hostscreenid){
                        $('td:eq(1)', nRow).html('<a href="http://11.111.111.11:8081/screen/'+aData.hostscreenid+'">'+aData.ip+'</a>');
                    }else{
                        $('td:eq(1)', nRow).html(aData.ip);
                    }

                    $('td:eq(6)', nRow).html("<span>线上</span>");
                }

                $('td:eq(9)', nRow).html('<a href="host.php?op=del&id='+aData.id+'"> <button class="btn btn-danger btn-sm">删除</button> </a> <button class="btn btn-success btn-sm" data-toggle="modal"data-target="#myModal'+aData.id+'">编辑 </button> ');
                return nRow;
            },

        }
    );

 服务器端php代码
 $sEcho = $_GET['sEcho'];
 $start = $_GET['iDisplayStart'];//从多少开始
 $length = $_GET['iDisplayLength'];//数据长度
 $sort_th = $_GET['iSortCol_0'];//被排序的列
 $sort_type = $_GET['sSortDir_0'];//排序规则

 if(!empty($_GET['sSearch'])){
     $search = $_GET['sSearch'];
 }

 $where = "";
 $order = "";
 if ($search) {
     $where = " where concat( xx,xx,xx,xx) like '%$search%' ";//查询
 }

 if ($sort_th == 1) {
     $order = " order by xx " . $sort_type . " ";
 } elseif ($sort_th == 2) {
     $order = " order by xx " . $sort_type . " ";
 } elseif ($sort_th == 4) {
     $order = " order by xx " . $sort_type . " ";
 } elseif ($sort_th == 4) {
     $order = " order by xx " . $sort_type . " ";
 } elseif ($sort_th == 5) {
     $order = " order by xx " . $sort_type . " ";
 } elseif ($sort_th == 6) {
     $order = " order by xx " . $sort_type . " ";
 } elseif ($sort_th == 8) {
     $order = " order by xx " . $sort_type . " ";
 }
 $condition = $where . $order;

 $hosts = getLimitRow("xx,xx,xx,xx", 'table', $condition, $start, $length);
 $count = getRecordCount('table');
 if(count($hosts) > 0){
     $host_screenid = getScreenid();
     foreach ($hosts as $index => $values) {
         foreach ($values as $field => $value) {
             if ($values['status'] == 0) {
                 $status_str = toutf8('线上');
             } else {
                 $status_str = toutf8('线下');
             }
             $aaData[$index][$field] = toutf8($value);
             $aaData[$index]['statusstr'] = $status_str;
             $aaData[$index]['hostscreenid'] = $host_screenid[$aaData[$index]['ip']];
         }
     }

     if ($search) {
         $dcount = getRecordCount('table', "where concat( xxx,xx,xx)    like '%$search%' ");
     } else {
         $dcount = $count;
     }
     $json_data = array('sEcho' => $sEcho, 'iTotalRecords' => $count, 'iTotalDisplayRecords' => $dcount, 'aaData' => $aaData);
     echo json_encode($json_data);
     exit;
 }else{
     $aaData = array();
     $json_data = array('sEcho' => $sEcho, 'iTotalRecords' => $count, 'iTotalDisplayRecords' => 0, 'aaData' => $aaData);
     echo json_encode($json_data);
 }