9行程式碼太浪費了，5行程式碼足矣，不用遞歸實現無限分類資料的樹狀格式化

我們知道很多開源軟體的無限分類都是採用遞歸的演算法，但是我們知道遞歸即浪費時間，又浪費空間（記憶體），
上次我也分享了個我自己原創的無限分類生成樹的方法，一熱心php高手網友給我提出了寶貴的建議，我測試了一下，這段代碼的時間非常之短，參考： http://www.oschina.net/code/snippet_98719_11296，我再次整理了一下，發現資料庫查詢出資料之後，我們就已經定好了鍵值，因而實踐中，我們一般會在model中查詢出格式化成主鍵值對應數據的形式，因而我們可以直接用這樣的數據，就少了一層循環。程式碼也非常簡潔。

/**
 * 此方法由@Tonton 提供
 * http://my.oschina.net/u/918697
 * @date 2012-12-12
*/
function genTree5($items) {
 foreach ($items as $item) )
 $items[$item['pid']]['son'][$item['id']] = &$items[$item['id']];
 回傳 isset($items[0]['son']) ？
}

/**
 * 將資料格式化成樹狀結構
 * @author Xuefen.Tong
 * @param array $items
 * @return array
*/
function genTree9($items) {
 $tree = array(); // 建構一棵樹
 foreach ($items as $item)
 if (isset($items[$item['pid']]))
 $items[$item['pid' ] ]['son'][] = &$items[$item['id']];
 else
 $tree[] = &$items[$item['id']];
返回$tree;
}

$items = array(
 1 => array('id' => 1, 'pid' => 0, 'name' => '江西省'),
 2 => array('id' => 2, 'pid' => 0, 'name' => '黑龍江省'),
 3 => array('id' => 3, 'pid' => 1, ' name' => '南昌市'),
 4 => array('id' => 4, 'pid' => 2, 'name' => '哈爾濱市'),
 5 => array ('id' => 5, 'pid' => 2, 'name' => '雞西市'),
 6 => array('id' => 6, 'pid' => 4, 'name ' => '香坊區'),
 7 => array('id' => 7, 'pid' => 4, 'name' => '南崗區'),
 8 => array ('id' => 8, 'pid' => 6, 'name' => '和興路'),
 9 => array('id' => 9, 'pid' => 7, ' name' => '西大直街'),
 10 => array('id' => 10, 'pid' => 8, 'name' => '東北林業大學'),
 11 => array('id' => 11, 'pid' => 9, 'name' => '哈爾濱工業大學'),
 12 => array('id' => 12, 'pid' => 8, 'name' => '哈爾濱師範大學'),
 13 => array('id' => 13, 'pid' => 1, 'name' => '趙州市'),
 14 => array('id' => 14, 'pid' => 13, 'name' => '贛縣'),
 15 => array('id' => 15, 'pid' => 13, 'name' => '於都縣'),
 16 => array('id' => 16, 'pid' => 14, 'name' => '茅店鎮'),
 17 => array('id' => 17, 'pid' => 14, 'name' => '大田鄉'),
 18 => array('id' => 18, 'pid' = > 16, 'name' => '義源村'),
 19 => array('id' => 19, 'pid' => 16, 'name' => '上壩村'),
);
echo "";
print_r(genTree5($items));
print_r(genTree9($items));

//後者輸出格式，前者類似，只是數組鍵值不一樣，不過不影響資料結構
/*
Array
(
[0] => Array
 (
 [id] => 1
 [pid] => 0
 [name] => 江西省
 [son] => Array
 (
 [0] => Array
 (
 [ id] => 3
 [pid] => 1
 [name] => 南昌市
 )

 [1] => Array
 (
 [id] => 13
 [pid] => 1
 [name] => 贛州市
 [son] => Array
 (
 [0] => Array
 (
 [id] => 14
 [pid] => 13
 [name] => 贛縣
 [son] => Array
 (
 [0] => Array
 (
 [id] => 16
 [pid] => 14
 [name] => 茅店鎮
 [son] => Array
 (
 [0] => Array
 (
 [id] => 18
 [pid] => 16
 [name] => 義源村
 )

 [1] = > Array
 (
 [id] => 19
 [pid] => 16
 [name] => 上壩村
 )

 )

 )

 [1] => Array
 (
 [id] => 17
 [pid] => 14
[name] => 大田鄉
 )

 )

 )

 [1] => Array
 (
 [id] => 15
                                        [pid] => 13
                                        [name] => 於都縣
                                    )

                            )

                    )

            )

 )

[1] => Array
 (
 [id] => 2
 [pid] => 0
 [name] => 黑龍江省
 [ son] => Array
 (
 [0] => Array
 (
 [id] => 4
 [pid] => 2
 [name] => 哈爾濱市
 [son] => Array
 (
 [0] => Array
 (
 [id] => 6
 [pid] => 4
 [name] => 香坊區
 [son] => Array
 (
 [0] => Array
 (
 [id] => 8
 [pid] => 6
 [name] => 和興路
 [son] => Array
 (
 [0] => Array
 (
 [id] => 10
 [pid ] => 8
 [name] =>
 東北林業大學
 )

 [1] => Array
 (
 [id] => 12
 [pid] => 8
 [name] =>
 哈爾濱師範大學
 )

 )

 )

 )

 )

 )
 )
 )

 [1] => Array
 (
 [id] => 7
 [pid] => 4
 [name] => 南崗區
 [ son] => Array
 (
 [0] => Array
 (
 [id] => 9
 [pid] => 7
 [name] => 西大直街
 [son] => Array
 (
 [0] => Array
 (
 [id] => 11
 [pid] => 9
 [ name] =>
                                                     哈爾濱工業大學
                                                    )

                                                )

                                            )

                                        )

                                )

                            )

 )

 [1] => Array ( [id] => 5 [pid] => 2[name] => 雞西市
                    )

            )

    )
)*/