Javascript-two-level interaction between thinkphp and ajax implementation drop-down list

Table Structure cId category idcName category name gid parent level id this is my HTML page & amp; lt; selectname & quot; gType & quot; id & quot; gType & quot; & amp; gt; {code ...} ajax code & amp; lt; script & amp; gt ;$ (& #039; # gType & #039 ;). click (function () {code ...}}); & amp; lt; script & amp; gt; thinkph... table Structure
CId category id
CName category name
Gid parent id
This is my HTML page
{$ Val. cName}

Ajax code
Script
$ ('# Gtype'). click (function (){

$(this).change(function(){    var objectModel = {};    var   value = $(this).val();   var   type = $(this).attr('id');    objectModel[gType] =value;    $.ajax({        cache:false,        type:"POST",        url:"/index.php/Goods/goodsAdd",        dataType:"json",        data:objectModel,        timeout:30000,        success:function(data){            $("#lables").empty();            var count = data.length;            var i = 0;            var b="";               for(i=0;i
  
   "+data[i].cName+"";               }            $("#lables").append(b);        }    });   });
  

}
);

Script
Thinkphp receiving page
Public function goodsAdd (){

    $model=M("category");            $rs=$model->where("pid=0")->select();    $this->assign("rs",$rs);    $this->display();    $result = array();    $cate =$_POST['gType'];    var_dump($cate);    $result = M('category')->where(array('pid'=> $cate))->field('cId,cName')->select();    var_dump($result);    $this->ajaxReturn($result,"JSON");        }

Where is the error? ajax is just getting started.

Reply content:

Table Structure
CId category id
CName category name
Gid parent id
This is my HTML page
{$ Val. cName}

Ajax code
Script
$ ('# Gtype'). click (function (){

$(this).change(function(){    var objectModel = {};    var   value = $(this).val();   var   type = $(this).attr('id');    objectModel[gType] =value;    $.ajax({        cache:false,        type:"POST",        url:"/index.php/Goods/goodsAdd",        dataType:"json",        data:objectModel,        timeout:30000,        success:function(data){            $("#lables").empty();            var count = data.length;            var i = 0;            var b="";               for(i=0;i
  
   "+data[i].cName+"";               }            $("#lables").append(b);        }    });   });
  

}
);

Script
Thinkphp receiving page
Public function goodsAdd (){

    $model=M("category");            $rs=$model->where("pid=0")->select();    $this->assign("rs",$rs);    $this->display();    $result = array();    $cate =$_POST['gType'];    var_dump($cate);    $result = M('category')->where(array('pid'=> $cate))->field('cId,cName')->select();    var_dump($result);    $this->ajaxReturn($result,"JSON");        }

Where is the error? ajax is just getting started.

What is your normal PHP code segment? Why display and ajaxReturn ..