php 三级联动菜单

代码如下：

-- 表的结构 `bigclass` 
-- 
CREATE TABLE `bigclass` ( 
`bigclassid` int(11) NOT NULL auto_increment, 
`bigclassname` varchar(200) collate utf8_unicode_ci NOT NULL, 
`sort` int(11) NOT NULL, 
`suoshu` int(1) NOT NULL, 
PRIMARY KEY (`bigclassid`) 
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=19 ; 
-- 表的结构 `smallclass` 
-- 
CREATE TABLE `smallclass` ( 
`smallclassid` int(11) NOT NULL auto_increment, 
`smallclassname` varchar(200) collate utf8_unicode_ci NOT NULL, 
`bigclassid` int(11) NOT NULL, 
`sort` int(11) NOT NULL, 
PRIMARY KEY (`smallclassid`) 
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=7 ; 
-- 表的结构 `minclass` 
-- 
CREATE TABLE `minclass` ( 
`minclassid` int(10) NOT NULL auto_increment, 
`minclassname` varchar(200) NOT NULL, 
`bigclassid` int(10) NOT NULL, 
`smallclassid` int(10) NOT NULL, 
`sort` int(10) NOT NULL, 
PRIMARY KEY (`minclassid`) 
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ;

代码如下：

<script language = "JavaScript"> 
var onecount; 
onecount=0; 
subcat = new Array(); 
<? 
//类别选择 
mysql_select_db($database_lr, $lr); 
$sql = "select * from smallclass order by sort"; 
$result = mysql_query( $sql ); 
$count = 0; 
while($res = mysql_fetch_row($result)){ 
?> 
subcat[<?=$count?>] = new Array("<?=$res[1]?>","<?=$res[4]?>","<?=$res[0]?>"); 
<? 
$count++; 
} 
?> 
onecount=<?php echo $count?> 
//联动函数 
function changelocation(bigclassid) 
{ 
document.myform.smallclassid.length = 0; 
var bigclassid=bigclassid; 
var i; 
document.myform.smallclassid.options[0] = new Option('请选择二级分类',''); 
for (i=0;i < onecount; i++) 
{ 
if (subcat[i][1] == bigclassid) 
{ 
document.myform.smallclassid.options[document.myform.smallclassid.length] = new Option(subcat[i][0], subcat[i][2]); 
} 
} 
} 
</script> 
<?php 
mysql_select_db($database_lr, $lr); 
$sql2 = "select * from minclass order by sort"; 
$result2 = mysql_query( $sql2 ); 
$count2 = 0; 
?> 
<script language = "JavaScript"> 
//如果这个数组中含有双引号则不能使用。即二级和三级类不能含有双引号 
var onecount2; 
onecount2=0; 
subcat2 = new Array(); 
<?php 
$count2 = 0; 
while($res2 = mysql_fetch_row($result2)){ 
?> 
subcat2[<?php echo $count2?>] = new Array("<?php echo $res2[1]?>","<?php echo $res2[3]?>","<?php echo $res2[0]?>"); 
<?php 
$count2++; 
} 
?> 
onecount2=<?php echo $count2?>; 
function changelocation2(smallclassid) 
{ 
document.myform.minclassid.length = 0; 
var smallclassid=smallclassid; 
var j; 
document.myform.minclassid.options[0] = new Option('请选择三级分类',''); 
for (j=0;j < onecount2; j++) 
{ 
if (subcat2[j][1] == smallclassid) 
{ 
document.myform.minclassid.options[document.myform.minclassid.length] = new Option(subcat2[j][0], subcat2[j][2]); 
} 
} 
} 
</script> 
<select name="bigclassid" onChange="changelocation(document.myform.bigclassid.options[document.myform.bigclassid.selectedIndex].value)" size="1"> 
<option selected value="">请指定一级分类</option> 
<? 
$sql = "select * from bigclass order by sort"; 
$result = mysql_query( $sql ); 
while($res = mysql_fetch_row($result)){ 
?> 
<option value="<? echo $res[0]; ?>"><? echo $res[1]?></option> 
<? } ?> 
</select> 
<select name="smallclassid" onChange="changelocation2(document.myform.smallclassid.options[document.myform.smallclassid.selectedIndex].value)" size="1"> 
<option selected value="">请指定二级分类</option> 
</select> 
<select name="minclassid" size="1"> 
<option selected value="">==所有三级分类==</option> 
</select>