XBOX

<script>
var obj_XML = false;

function Send_Request()
{
    obj_XML = GetXMLHttpRequest();
 
 if (!obj_XML) {
     alert("不能创建XMLHttpRequest对象");
 
     return false;
 }
 
 url = "test.php?cityid=all";
 obj_XML.open("GET", url, true);
 obj_XML.onreadystatechange = ProcessDate;
 obj_XML.send(null);
}

function ProcessDate()
{
    if (obj_XML.readyState == 4) {
     if (obj_XML.status == 200) {
      Splicity(obj_XML.responseText);
   //document.getElementById('msg').innerHTML = obj_XML.responseText;
  } else {
      alert("no data come back");
  }
 }
}

function Splicity(rs)
{
    document.form1.city.length = 0;
 document.form1.city.add(new Option("--请选择--", 0));
    var field = rs.split(";");
 
 for (var i=0; i<field.length; i++) {
     var subfield = field[i];
  var op       = subfield.split(",");
  
  if (op[0] !='') {
      document.form1.city.add(new Option(op[1], op[0]));
  }
 }
}

function ChangeTown(id)
{
    obj_XML = GetXMLHttpRequest();
 
 if (!obj_XML) {
     alert("不能创建XMLHttpRequest对象");
 
     return false;
 }
 
 url = "test.php?cityid=" + id;
 obj_XML.open("GET", url, true);
 obj_XML.onreadystatechange = FillTown;
 obj_XML.send(null);
}

function FillTown()
{
    if (obj_XML.readyState == 4) {
     if (obj_XML.status == 200) {
      Splitown(obj_XML.responseText);
   //document.getElementById('msg').innerHTML = obj_XML.responseText;
  } else {
      alert("no data come back");
  }
 }
}

function Splitown(rs)
{
    document.form1.town.length = 0;
    var field = rs.split(";");
 
 for (var i=0; i<field.length; i++) {
     var subfield = field[i];
  var op       = subfield.split(",");
  
  if (op[0] !='') {
      document.form1.town.add(new Option(op[1], op[0]));
  }
 }
}

function GetXMLHttpRequest()
{
    var xmlHttp = false;
 
 if (window.XMLHttpRequest) {
    // xmlHttp = new XMLHttpRequest();
 } else if (window.ActiveXObject) {
     try {
      xmlHttp = new ActiveXObject("msxml2.xmlhttp");
  } catch (e) {
      try {
          xmlHttp = new ActiveXObject("micsofot.xmlhttp");
   } catch (e) {
   }
  }
 }
 
 return xmlHttp;
}

<form name="form1" action="" method="get">
 <table width="200" border="0" cellpadding="0" cellspacing="0">
  <tr>
   <td>City:<select name="city" onchange="ChangeTown(this.value)">          
            </select></td>
   <td>Town:<select name="town">
                         <option>--请选择--</option>
                        </select>
   </td>
  </tr>
 </table>
</form>
-------------------------------------------------
<?php
header("Content-type: text/html; charset=utf-8");
$cid = $_GET['cityid'];

$link_id = mysql_connect('localhost', 'root', 'dingran');

if (!$link_id) {
    echo mysql_error();

    return false;
}

mysql_query('set names utf8');
mysql_select_db('menu');

if ($cid == 'all') {
    $sql = "SELECT id, name FROM city";
 $result = mysql_query($sql, $link_id);
 
 if (mysql_num_rows($result) > 0) {
     while ($rows = mysql_fetch_array($result)) {
      echo $rows[0] . ',' . $rows[1] . ';';
  }
 }
} elseif ($cid == '0') {
    echo '0' . ',' . '--请选择--' . ';';
  } else {
    $sql = "SELECT id, name FROM town Where c_id = " . $cid;
 $result = mysql_query($sql, $link_id);
 
 if (mysql_num_rows($result) > 0) {
     while ($rows = mysql_fetch_array($result)) {
      echo $rows[0] . ',' . $rows[1] . ';';
  }
 }
}
?>