Ajax+php realizes three-level linkage of product classification

$(function(){
  //请求路径
  var url="03goods.php";
  //option默认内容
  var option="<option value=&#39;0&#39;>未选择</option>";
  //获取jq对象
  var $sel1=$(".sel1");
  var $sel2=$(".sel2");
  var $sel3=$(".sel3");
  //自动生成一个<option>元素
  function createOption(value,text){
  var $option=$("<option></option>");
  $option.attr("value",value);
  $option.text(text);
  return $option;
  }
  //加载数据
  function ajaxSelect($select,id){
  //get请求
  $.get(url,{"pid":id},function(data){
   $select.html(option);
   for(var k in data ){
   $select.append(createOption(data[k].id,data[k].name));
   }
  },"json");
  }

  //自动加载第一个下拉菜单
  ajaxSelect($sel1,"0");

  //选择第一个下拉菜单时加载第二个
  $sel1.change(function(){
  var id=$sel1.val();
  if(id=="0"){
   $sel2.html(option);
   $sel3.html(option);
  }else{
   ajaxSelect($sel2,id);
  }
  });

  //选择第二个下拉菜单时加载第三个
  $sel2.change(function(){
  var $id=$sel2.val();
  if($id=="0"){
   $sel3.html(option);
  }else{
   ajaxSelect($sel3,$id);
  }
  });
 });

<?php
 header(&#39;Content-Type:text/html; charset=utf-8&#39;);
 //数据
 $arr=array(
 //array(分类id,分类名，分类的父id)
 array(&#39;id&#39;=>&#39;1&#39;,&#39;name&#39;=>&#39;数码产品&#39;,&#39;pid&#39;=>&#39;0&#39;),
 array(&#39;id&#39;=>&#39;2&#39;,&#39;name&#39;=>&#39;家电&#39;,&#39;pid&#39;=>&#39;0&#39;),
 array(&#39;id&#39;=>&#39;3&#39;,&#39;name&#39;=>&#39;书籍&#39;,&#39;pid&#39;=>&#39;0&#39;),
 array(&#39;id&#39;=>&#39;4&#39;,&#39;name&#39;=>&#39;服装&#39;,&#39;pid&#39;=>&#39;0&#39;),
 array(&#39;id&#39;=>&#39;5&#39;,&#39;name&#39;=>&#39;手机&#39;,&#39;pid&#39;=>&#39;1&#39;),
 array(&#39;id&#39;=>&#39;6&#39;,&#39;name&#39;=>&#39;笔记本&#39;,&#39;pid&#39;=>&#39;1&#39;),
 array(&#39;id&#39;=>&#39;7&#39;,&#39;name&#39;=>&#39;平板电脑&#39;,&#39;pid&#39;=>&#39;1&#39;),
 array(&#39;id&#39;=>&#39;8&#39;,&#39;name&#39;=>&#39;智能手机&#39;,&#39;pid&#39;=>&#39;5&#39;),
 array(&#39;id&#39;=>&#39;9&#39;,&#39;name&#39;=>&#39;功能机&#39;,&#39;pid&#39;=>&#39;5&#39;),
 array(&#39;id&#39;=>&#39;10&#39;,&#39;name&#39;=>&#39;电视机&#39;,&#39;pid&#39;=>&#39;2&#39;),
 array(&#39;id&#39;=>&#39;11&#39;,&#39;name&#39;=>&#39;电冰箱&#39;,&#39;pid&#39;=>&#39;2&#39;),
 array(&#39;id&#39;=>&#39;12&#39;,&#39;name&#39;=>&#39;智能电视&#39;,&#39;pid&#39;=>&#39;10&#39;),
 array(&#39;id&#39;=>&#39;13&#39;,&#39;name&#39;=>&#39;编程书籍&#39;,&#39;pid&#39;=>&#39;3&#39;),
 array(&#39;id&#39;=>&#39;14&#39;,&#39;name&#39;=>&#39;JavaScript&#39;,&#39;pid&#39;=>&#39;13&#39;),
 );
 //获取指定分类的商品
 function getByPid($arr,$pid){
 $result=array();
 foreach($arr as $v){
  if($v[&#39;pid&#39;]==$pid){
  $result[]=$v;
  }
 }
 return $result;
 }
 //获取请求参数
 $pid=isset($_GET[&#39;pid&#39;])?$_GET[&#39;pid&#39;]:&#39;0&#39;;

 $result=getByPid($arr,$pid);
 //输出json数据
 echo json_encode($result);
?>