$data = array (
 0 => 
 array (
 'id' => '1',
 'name' => 'WEB编程',
 'parentid' => '0',
 ),
 1 => 
 array (
 'id' => '2',
 'name' => 'PHP',
 'parentid' => '1',
 ),
 2 => 
 array (
 'id' => '3',
 'name' => 'Ajax',
 'parentid' => '1',
 ),
 3 => 
 array (
 'id' => '4',
 'name' => 'java',
 'parentid' => '1',
 ),
 4 => 
 array (
 'id' => '5',
 'name' => 'WinForm编程',
 'parentid' => '0',
 ),
 5 => 
 array (
 'id' => '6',
 'name' => 'VB',
 'parentid' => '5',
 ),
 6 => 
 array (
 'id' => '7',
 'name' => 'VC',
 'parentid' => '5',
 ),
);

这么一个数组，想得到下面的效果。

<select name="categorys">
 <optgroup label="WEB编程">
 <option value="2" >PHP</option>
 <option value="3" >Ajax</option>
 <option value="4" >java</option>
 </optgroup>
 
 <optgroup label="WinForm编程">
 <option value="6" >VB</option>
 <option value="7" >VC</option>
 </optgroup>
</select>

难点在于如何在foreach里判断把<option>包含在<optgroup>里，折腾了半天也没出办法。请高手指点如何完成。

$data = array (
 0 => array (
 'id' => '1',
 'name' => 'WEB编程',
 'parentid' => '0',
 ),
 1 => array (
 'id' => '2',
 'name' => 'PHP',
 'parentid' => '1',
 ),
 2 => array (
 'id' => '3',
 'name' => 'Ajax',
 'parentid' => '1',
 ),
 3 => array (
 'id' => '4',
 'name' => 'java',
 'parentid' => '1',
 ),
 4 => array (
 'id' => '5',
 'name' => 'WinForm编程',
 'parentid' => '0',
 ),
 5 => array (
 'id' => '6',
 'name' => 'VB',
 'parentid' => '5',
 ),
 6 => array (
 'id' => '7',
 'name' => 'VC',
 'parentid' => '5',
 ),
);
 
echo '<select name="categorys">';
foreach($data as $v) {
 if($v['parentid'] == 0)
 echo "<optgroup label='$v[name]'>";
 else
 echo "<option value='$v[id]' >$v[name]</option>";
}
echo '</select>';

唠叨大哥，你上面的操作还是缺了结束符啊</optgroup>

我就是在苦闷如何把这个</optgroup>加进去。

echo "<optgroup label='$v[name]'>$v[name]</optgroup>";

稍微改下就行了。

$data = array (
 0 => 
 array (
 'id' => '1',
 'name' => 'WEB编程',
 'parentid' => '0',
 ),
 1 => 
 array (
 'id' => '2',
 'name' => 'PHP',
 'parentid' => '1',
 ),
 2 => 
 array (
 'id' => '3',
 'name' => 'Ajax',
 'parentid' => '1',
 ),
 3 => 
 array (
 'id' => '4',
 'name' => 'java',
 'parentid' => '1',
 ),
 4 => 
 array (
 'id' => '5',
 'name' => 'WinForm编程',
 'parentid' => '0',
 ),
 5 => 
 array (
 'id' => '6',
 'name' => 'VB',
 'parentid' => '5',
 ),
 6 => 
 array (
 'id' => '7',
 'name' => 'VC',
 'parentid' => '5',
 ),
);
$tempArray = array();
foreach($data as $item){
 $tempArray[$item['parentid']][$item['id']] = $item['name'];
}
echo '<select name="categorys">';
foreach($tempArray[0] as $parentid=>$name){
 echo "<optgroup label=\"$name\">";
 foreach($tempArray[$parentid] as $id=>$name){
 echo "<option value=\"$id\" >$name</option>";
 }
 echo '</optgroup>';
}
echo '</select>';

只是foreach了三次怕效率较差，不知还没有有别的方法。

重做数组的话……

$data = array (
 array (
 'id' => '1',
 'name' => 'WEB编程',
 'parentid' => '0',
 'sub'=>
 array(
 array(
 'id' => '2',
 'name' => 'PHP',
 'parentid' => '1',
 ),
 array (
 'id' => '3',
 'name' => 'Ajax',
 'parentid' => '1',
 ),
 array (
 'id' => '4',
 'name' => 'java',
 'parentid' => '1',
 )
 )
 ),
 array (
 'id' => '5',
 'name' => 'WinForm编程',
 'parentid' => '0',
 'sub'=>
 array(
 array (
 'id' => '6',
 'name' => 'VB',
 'parentid' => '5',
 ),
 array (
 'id' => '7',
 'name' => 'VC',
 'parentid' => '5',
 )
 )
 )
);
echo '<select style="width:200px;">';
for($i=0,$il=count($data);$i<$il;$i++){
 echo '<optgroup label="'.$data[$i]['name'].'">';
 for($j=0,$jl=count($data[$i]['sub']);$j<$jl;$j++){
 echo '<option>'.$data[$i]['sub'][$j]['name'].'</option>';
 }
 echo '<optgroup>';
}
echo '</select>';

是吗？
哦，是少了个 </optgroup>
不过我测试代码时并没有感觉出有与没有的差异

一定要有的话，就加个开关变量。要多次循环干什么？

echo '<select name="categorys">';
$k = false;
foreach($data as $v) {
 if($v['parentid'] == 0) {
 echo "<optgroup label='$v[name]'>";
 $k = true;
 }else {
 if($k) echo '</optgroup>';
 echo "<option value='$v[id]' >$v[name]</option>";
 $k = false;
 }
}
echo '</select>';