PHP数组分级，万般无奈，救助
array (
array("level" => '1', "caption" => "一级菜单1"),
array("leve1" => '1', "caption" => "一级菜单2"),
array("leve1" => '2', "caption" => "二级菜单1"),
array("leve1" => '2', "caption" => "二级菜单2"),
array("leve1" => '1', "caption" => "一级菜单3"),
)
其中level = 2为其上方最近leve1 = 1 的子菜单，不排除会有level = 3的子菜单(从属于level = 2)现在想弄成下面的形式，想了好久也没什么好方法，同事建议我用递归，可递归小弟不太懂，PHP初接触，给各位大拿添麻烦了
array (
array("level" => '1', "caption" => "一级菜单1"),
array("leve1" => '1', "caption" => "一级菜单2",
"sub"=>array("leve1" => '2', "caption" => "二级菜单1"),
"sub"=>array("leve1" => '2', "caption" => "二级菜单2")
),
array("leve1" => '1', "caption" => "一级菜单3"),
)
<br>
<br>
<br>
$arr = array(<br>
<br>
array('id'=>1,'city_name'=>'中国','rel_id'=>'1','pid'=>0),<br>
array('id'=>2,'city_name'=>'广东','rel_id'=>'1-2','pid'=>1),<br>
array('id'=>3,'city_name'=>'深圳','rel_id'=>'1-2-3','pid'=>2),<br>
array('id'=>4,'city_name'=>'广州','rel_id'=>'1-2-4','pid'=>2)<br>
<br>
);<br>
<br>
function find_subclass( $pid ){<br>
<br>
global $arr;<br>
$__arr = array();<br>
foreach ( $arr as $k=>$v )<br>
{<br>
<br>
if( $v['pid']==$pid )$__arr[] = $v;<br>
<br>
}<br>
return $__arr;<br>
<br>
}<br>
<br>
function tree_subclass($pid=0){<br>
<br>
$__arr = array();<br>
$__arr = find_subclass($pid);<br>
if( !empty($__arr) ){<br>
<br>
foreach ( $__arr as $k=>$v )<br>
{ <div class="clear">
</div>
