啊，最后有一些参考文献很方便：
<?PHP
$tree = array(
array('Cat 1', 'depth' => 0),
array('Cat 2', 'depth' => 1),
array('Cat 3', 'depth' => 1),
array('Cat 4', 'depth' => 2),
array('Cat 5', 'depth' => 1),
array('Cat 6', 'depth' => 2),
array('Cat 7', 'depth' => 3),
array('Cat 8', 'depth' => 1)
);
//same as before
$currDepth = -1;
//initilialize result
$result = array();
//create path structure for depths
$path = array();
//create 'root' node
$olditem = array('children'=> &$result);
foreach($tree as $item){
if($item['depth'] > $currDepth){
//remove possible old reference (old depth of other branch
if(isset($path[$item['depth']])) unset($path[$item['depth']]);
//make sure we have an array entry
if(!isset($olditem['children'])) $olditem['children'] = array();
//acquire target
$path[$item['depth']] = &$olditem['children'];
}
if($item['depth'] != $currDepth) unset($olditem);
//set correct target
$currDepth = $item['depth'];
//add item
$path[$currDepth][] = &$item;
//copy & remove reference
$olditem = &$item;
unset($item);
}
//always nice to clean up reference bombs:
unset($path);
unset($olditem);
var_dump($result);
?>
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