Ajax实现城市二级联动（三）

<select id="province"> <option>请选择</option> </select> <select id="city"> <option>请选择</option> </select>

//创建获取ajax核心对象的函数  function getXhr(){   var xhr = null;   if(window.XMLHttpRequest){    xhr = new XMLHttpRequest();   }else{    xhr = new ActiveXObject("Microsoft.XMLHttp");   }   return xhr;  }  var xhr = getXhr();  // 第一次执行Ajax异步请求 - 省份  window.onload = function(){   xhr.open("get","finaly.php?state=1");   xhr.send(null);   xhr.onreadystatechange = function(){   if(xhr.readyState==4&&xhr.status==200){     var data = xhr.responseText;     // 将字符串转换为数组     var provinces = data.split(",");     // 遍历数组     for(var i=0;i<provinces.length;i++){      // 创建option元素添加到id为province元素上      var option = document.createElement("option");      var text = document.createTextNode(provinces[i]);      option.appendChild(text);      var province = document.getElementById("province");      province.appendChild(option);     }    }    }  };  // 第二次执行Ajax异步请求 - 城市  var province=document.getElementById("province");  province.onchange = function(){   var city = document.getElementById("city");   var opts = city.getElementsByTagName("option");   for(var z=opts.length-1;z>0;z--){    city.removeChild(opts[z]);   }   if(province.value != "请选择"){    xhr.open("post","finaly.php");    xhr.setRequestHeader("Content-Type","application/x-www-form-urlencoded");    xhr.send("state=2&province="+province.value);    xhr.onreadystatechange = function(){     if(xhr.readyState==4&&xhr.status==200){      var data = xhr.responseText;      var cities = data.split(",");      for(var i=0;i<cities.length;i++){       var option = document.createElement("option");       var text = document.createTextNode(cities[i]);       option.appendChild(text);       city.appendChild(option);      }     }    }   }  };

<?php // 接收客户端发送的请求数据 - state $state = $_REQUEST['state']; // 判断$state的值 if($state == 1){// 获取省份  echo '山东省,辽宁省,吉林省'; }else{// 获取城市  $province = $_POST['province'];  switch ($province){   case '山东省':    echo '青岛市,济南市,威海市,日照市,德州市';    break;   case '辽宁省':    echo '沈阳市,大连市,铁岭市,丹东市,锦州市';    break;   case '吉林省':    echo '长春市,松原市,吉林市,通化市,四平市';    break;  } }?>