PHP+mysql实现的三级联动菜单功能示例

-- 数据库: `student`
--
-- --------------------------------------------------------
--
-- 表的结构 `student`
--
CREATE TABLE `student` (
 `id` int(50) NOT NULL auto_increment,
 `name` varchar(50) collate utf8_unicode_ci NOT NULL,
 `dept` varchar(50) collate utf8_unicode_ci NOT NULL,
 `class` varchar(50) collate utf8_unicode_ci NOT NULL,
 `sex` varchar(50) collate utf8_unicode_ci NOT NULL,
 `dept_id` int(50) NOT NULL,
 `class_id` int(50) NOT NULL,
 PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=5 ;
--
-- 导出表中的数据 `student`
--
INSERT INTO `student` (`id`, `name`, `dept`, `class`, `sex`, `dept_id`, `class_id`) VALUES
(1, '计算机名字', '计算机工程系', '计061', '男', 1, 11),
(2, '教计名字', '计算机工程系', '教技061', '男', 1, 14),
(3, '管理名字', '管理系', '管理061', '女', 2, 21),
(4, '机械名字', '机械工程系', '自动化061', '男', 3, 31);

?php
$link=mysql_connect("localhost","root","") or die("数据库服务器连接错误".mysql_error());
mysql_select_db("student",$link) or die("数据库访问错误".mysql_error());
mysql_query("set character set gb2312");
mysql_query("set names gb2312");
?>
html>
 head>
 title>下拉框连动/title>
 /head>
body>
script language="JavaScript">
//二级菜单数组
var subcat = new Array();
?php
$i=0;
$sql="select * from student";
$query=mysql_query($sql,$link);
while($arr=mysql_fetch_array($query))
{
 echo "subcat[".$i++."] = new Array('".$arr["dept_id"]."','".$arr["class"]."','".$arr["class_id"]."');\n";
}
?>
//三级菜单数组
var subcat2 = new Array();
?php
$i=0;
$sql="select * from student";
$query=mysql_query($sql,$link);
while($arr=mysql_fetch_array($query))
{
 echo "subcat2[".$i++."] = new Array('".$arr["class_id"]."','".$arr["class"]."','".$arr["name"]."');\n";
}
?>
function changeselect1(locationid)
{
 document.form1.s2.length = 0;
 document.form1.s2.options[0] = new Option('22请选择22','');
 for (i=0; isubcat.length; i++)
 {
 if (subcat[i][0] == locationid)
 {
  document.form1.s2.options[document.form1.s2.length] = new Option(subcat[i][1], subcat[i][2]);
 }
 }
}
function changeselect2(locationid)
{
 document.form1.s3.length = 0;
 document.form1.s3.options[0] = new Option('33请选择33','');
 for (i=0; isubcat2.length; i++)
 {
 if (subcat2[i][0] == locationid)
 {
  document.form1.s3.options[document.form1.s3.length] = new Option(subcat2[i][2], subcat2[i][0]);
 }
 }
}
/script>三级联动演示：BR>
form name="form1">
select name="s1" onChange="changeselect1(this.value)">
option>--请选择--/option>
option value=1>计算机工程系/option>
option value=2>管理系/option>
option value=3>机械工程系/option>
/select>
select name="s2" onChange="changeselect2(this.value)">
 option>--请选择--/option>
/select>
select name="s3">
 option>--请选择--/option>
/select>
/form>
/body>
/html>