三级联动

页面：

<select  name="xqcate1" id="xqcate1" style="margin-left:20px;width:150px;color:black;" class="form-control m-b chosen-select">
    <option value="">==请选择==</option>

</select>

<select  name="xqcate2" id="xqcate2" style="margin-left:20px;width:150px;color:black;" class="form-control m-b chosen-select">
    <option value="">==请选择==</option>

</select>

控制器：

//三级联动
public function san()
{
        $xqcate = input("xqcate");
        $da = Db::name('xqcate')->where('pid', $xqcate)->select();

        if (count($da) > 0) {
            echo json_encode(array('code'=>200,'info'=>$da));
            exit;
        }else{
            echo json_encode(array('code'=>400));
        }
}

//三级联动
public function four()
{
    $xqcate1 = input("xqcate1");
    $dat = Db::name('xqcate')->where('pid', $xqcate1)->select();

    if (count($dat) > 0) {
        echo json_encode(array('code'=>200,'info'=>$dat));
        exit;
    }else{
        echo json_encode(array('code'=>400));

    }
}

ajax：

$("#xqcate").change(function () {
    var xqcate = $(this).val();
    $.ajax({
        url: "/otadmins/achievement/san",
        Type: "POST",
        data: {xqcate: xqcate},
        dataType: "JSON",
        success: function (data) {
            $('#xqcate1').empty();
            $('#xqcate2').html('<option value="">==请选择==</option>');
            var html = '<option value="">==请选择==</option>';
            if (data.code == 200) {
                $.each(data.info,function(index,comment){

                    html += "<option value='"+comment['id']+"'>"+comment['name']+"</option>";
                });
            }
            $('#xqcate1').append(html);
        }
    });
});


$("#xqcate1").change(function () {
    var xqcate = $(this).val();
    $.ajax({
        url: "/otadmins/achievement/san",
        Type: "POST",
        data: {xqcate: xqcate},
        dataType: "JSON",
        success: function (data) {
            $('#xqcate2').empty();
            var html = '<option value="">==请选择==</option>';
            if (data.code == 200) {
                $.each(data.info,function(index,comment){

                    html += "<option value='"+comment['id']+"'>"+comment['name']+"</option>";
                });
            }
            $('#xqcate2').append(html);
        }
    });
});