三级联动+ThinkPHP

1、前端HTML代码

<div class="layui-form-item">
                <label for="level1" class="layui-form-label">
                    <span class="x-red">*</span>商品一级分类</label>
                <div class="layui-input-inline">
                    <select id="level1" name="level1" class="valid" lay-filter="level1">
                        <option value="0">请选择</option>
                        {foreach $level1 as $v}
                        <option value="{$v.id}">{$v.cate_name}</option>
                        {/foreach}
                    </select>
                </div>
                <div class="layui-input-inline">
                    <select id="level2" name="level2" class="valid" lay-filter="level2">

                    </select>
                </div>
                <div class="layui-input-inline">
                    <select id="level3" name="cate_id" class="valid">

                    </select>
                </div>
            </div>

2、前端JS代码

function changeCate(args1,args2){
            form.on('select('+args1+')',function (data) {
                // 获取一级分类id
                var id = data.value;
                if(id == 0){
                    $("#"+args2).html("");
                    form.render();
                    return false;
                }
                // 根据一级分类id 查询二级分类
                $.get("{:url('getSon')}",{id:id},function (data) {
                    var str = "<option value='0'>请选择</option>";
                    for(var i=0;i<data.sons.length;i++){
                        str += "<option value='"+data.sons[i].id+"'>"+data.sons[i].cate_name+"</option>";
                    }
                    $("#"+args2).html(str);
                    form.render();
                },"json");
            });
        }
        changeCate('level1','level2');
        changeCate('level2','level3');

3、后端PHP代码

public function create(){
        // 获取一级分类
        $level1 = Db::name("category")->where("pid",0)->order("id")->select();
        $data = compact("level1");
        return view("",$data);
    }
    // 获取二级分类
    public function getSon($id){
        $data['sons'] = Db::name("category")->where(["pid"=>$id])->select();
        $data['sql'] = Db::getLastSql();
        return json($data);
    }