layui的checkbox选中赋值

 $(".w_bianji").click(function () {
            var formData = new FormData(document.getElementById("tf"));//表单id
            var preloading =  $("input[name='preloading']").attr("checked"); //选中
            if(preloading  != 'checked'){
                preloading = 0;        //赋值
                formData.append("preloading",preloading);
            }    
            $.ajax({
                url: '',
                type: 'POST',
                data: formData,
                async: false,
                cache: false,
                contentType: false,
                processData: false,
                success: function (data) {
                   
                    var data = JSON.parse(data);
                    console.log(data.msg);
                   layer.msg(data.msg);
                }
            });

js  通过监听这个事件 

        layui.use(['laypage', 'layer', 'element', 'form'], function () {
        var laypage = layui.laypage,
            element = layui.element,
            form = layui.form
            form.on('checkbox('name值')',function(obj){
                    if(obj.elem.checkbox == true){
                          //可以打印
                        console.log(obj.elem.checkbox);
                        }
                })
    })

php     可以在控制接受 然后判断改变值

        $sp_state = @$data['sp_state']; 
			if ($sp_state == 'on') { 
				$data['sp_state'] = 1; //设置上限 
			} else { 
				$data['sp_state'] = 9; //无上限 
			}