簡単な再帰法を教えてください

$arr = array(
array(
'id' => 1,
'parentid' => 0,
'title' => 'a'
),
array(
'id' => 2,
'parentid' => 1,
'title' => 'a-1'
),
array(
'id' => 3,
'親 ID' => 1,
'タイトル' => 'a-1'
),
array(
'id' => 4,
'parentid' => 2,
'title' => 'a-1-1
)
);

递归转换は数组如下:
$arr = array(
'id' => 1,
'parentid' => 0,
'タイトル' => 'a',
'子' =＆gt; array（
'id' =＆gt; 2、 'parentid' =＆gt; 'title' =＆gt; 'a-1' =＆gt; array .....
）Array（
'id' =＆gt; 3、
'dartid' =＆gt; 2、
'title' =＆gt; 'a-2'
）、
.... .... ..
);
请问要 どのように写しますか?

ディスカッションへの返信 (解決策)

function findChildren($list, $p=0){  $r = array();  foreach($list as $id=>$item){    if($item['parentid'] == $p) {      $r[$id] = $item;      if($t = findChildren($list, $item['id']) )        $r[$id]['children'][] = $t;    }  }  return $r;}        $arr = array(    array(        'id' => 1,        'parentid' => 0,        'title' => 'a'    ),    array(        'id' => 2,        'parentid' => 1,        'title' => 'a-1'    ),    array(        'id' => 3,        'parentid' => 1,        'title' => 'a-1'    ),    array(        'id' => 4,        'parentid' => 2,        'title' => 'a-1-1'    )  );print_r(findChildren($arr));

Array
(
[0] => Array
(
[id] => 1
[parent ] id] => 0
] = & Gt;
[0] = & gt; 配列
(
[1] = & gt; 配列
(
[id] = & gt; 2
[paintid] = & gt; 1
[title] = & gt; a- 1
;                                                            [タイトル] => a-1-1
)
)

)
)
[2] => array
（
[id] =＆gt; 3
[dartid] =＆gt; 1
[title] =＆gt; a-1
）
）