数据表结构：
/* 表结构
--
-- 表的结构 `web_city`
--
CREATE TABLE IF NOT EXISTS `web_city` (
`id` mediumint(8) NOT NULL AUTO_INCREMENT,
`title` varchar(60) NOT NULL,
`pid` mediumint(8) NOT NULL DEFAULT '0',
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=5 ;
--
-- 转存表中的数据 `web_city`
--
INSERT INTO `web_city` (`id`, `title`, `pid`) VALUES
(1, '北京', 0),
(2, '东单', 1),
(3, '西单', 1);
*/php代码：
<?php
$my_db = mysql_connect("localhost","root","");
mysql_select_db("city", $my_db);
mysql_query("set names 'utf8'");
$sql = "select * from web_city where pid = 0";
$query = mysql_query($sql);
$provice = array();
while($row = mysql_fetch_assoc($query))
{
$provice[] = $row;
}
?>
引入jquery-1.8.0.min.js 自己下载
html代码：
<script>
function select_city(){
var id = jQuery("#provice option:selected").val();
$("#city").html('<option value="">选择市</option>');
$.ajax({
type: "post",
url: "ajax.php",
data: "id="+id,
dataType: "json",
success: function(msg){
var tbody = "";
$.each(msg.optionss,function(n,value){
var trs = "";
trs += "<option value='"+ value.id +"'>"+value.title+"</option>";
tbody += trs;
})
$("#city").append(tbody);
}
});
}
</script>
<div>
<select name="provice" id="provice" onchange="select_city()">
<option value="">选择省/市</option>
<?php foreach($provice as $val){?>
<option value="<?php echo $val['id'];?>"><?php echo $val['title'];?></option>
<?php }?>
</select>
<select name="city" id="city">
<option value="">选择市</option>
</select>
</div>以下代码为 ajax.php
<?php
$my_db = mysql_connect("localhost","root","");
mysql_select_db("city", $my_db);
mysql_query("set names 'utf8'");
if(isset($_POST['id'])){
$id = $_POST['id'];
$sql_city = "select * from web_city where pid = $id";
$query_city = mysql_query($sql_city);
$city = array();
while($row = mysql_fetch_assoc($query_city))
{
$city[] = $row;
}
echo json_encode(array('optionss'=>$city));
}
?>