php FLEA中二叉树数组的遍历输出

但是要怎样遍历这个方法产生的二叉树数组呢？以下是我的做法：

<?php 
function preTree($cat){ 
foreach ($cat as $c){ 
?> 
<p><a href="http://<?=$c['poper_site']?>"><?=$c['poper']?></a>:<?=t($c['content'])?></p> <?php if(isset($c['childrens'])){?> 
<ul> 
<?php foreach ($c['childrens'] as $s){?> 
<li><p><a href="http://<?=$s['poper_site']?>"><?=$s['poper']?></a>:<?=t($s['content'])?></p> 
<?php 
if(isset($s['childrens'])){ 
?><ul><li><?php 
$this->preTree($s['childrens']); 
?></li></ul><?php 
} 
?> 
</li> 
<?php }?> 
</ul> 
<?php }?> 
<?php 
} 
} 
?>