php 无限分类 树形数据格式化代码

我们知道很多开源软件的无限分类都是采用递归的算法，但是我们知道递归即浪费时间，又浪费空间（内存），
上次我也分享了个我自己原创的无限分类生成树的方法，一热心php高手网友给我提出了宝贵的建议，我测试了一下，这段代码的时间非常之短参考： http://www.oschina.net/code/snippet_98719_11296，我再次整理了一下，发现数据库查询出数据之后，我们就已经定好了键值，因而实践中，我们一般会在model中查询出格式化成主键值对应数据的形式，因而我们可以直接用这样的数据，就少了一层循环。代码也非常简洁。

原来的代码：

function genTree($items,$id='id',$pid='pid',$son = 'children'){  $tree = array(); //格式化的树  $tmpMap = array(); //临时扁平数据     foreach ($items as $item) {    $tmpMap[$item[$id]] = $item;  }     foreach ($items as $item) {    if (isset($tmpMap[$item[$pid]])) {      $tmpMap[$item[$pid]][$son][] = &$tmpMap[$item[$id]];    } else {      $tree[] = &$tmpMap[$item[$id]];    }  }  unset($tmpMap);  return $tree;} $items1 = array(    array('id' => 1, 'pid' => 0, 'name' => '一级11' ),    array('id' => 11, 'pid' => 0, 'name' => '一级12' ),    array('id' => 2, 'pid' => 1, 'name' => '二级21' ),    array('id' => 10, 'pid' => 11, 'name' => '二级22' ),    array('id' => 3, 'pid' => 1, 'name' => '二级23' ),    array('id' => 12, 'pid' => 11, 'name' => '二级24' ),    array('id' => 9, 'pid' => 1, 'name' => '二级25' ),    array('id' => 14, 'pid' => 1, 'name' => '二级26' ),    array('id' => 4, 'pid' => 9, 'name' => '三级31' ),    array('id' => 6, 'pid' => 9, 'name' => '三级32' ),    array('id' => 7, 'pid' => 4, 'name' => '四级41' ),    array('id' => 8, 'pid' => 4, 'name' => '四级42' ),    array('id' => 5, 'pid' => 4, 'name' => '四级43' ),    array('id' => 13, 'pid' => 4, 'name' => '四级44' ),    array('id' => 15, 'pid' => 8, 'name' => '五级51' ),    array('id' => 16, 'pid' => 8, 'name' => '五级52' ),    array('id' => 17, 'pid' => 8, 'name' => '五级53' ),    array('id' => 18, 'pid' => 16, 'name' => '六级64' ),); var_dump(genTree($items1));

以下是补充：

/** * 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[$item['id']];  return isset($items[0]['son']) ? $items[0]['son'] : array();}

/** * 将数据格式化成树形结构 * @author Xuefen.Tong * @param array $items * @return array */function genTree9($items) {  $tree = array(); //格式化好的树  foreach ($items as $item)    if (isset($items[$item['pid']]))      $items[$item['pid']]['son'][] = &$items[$item['id']];    else      $tree[] = &$items[$item['id']];  return $tree;} $items = array(  1 => array('id' => 1, 'pid' => 0, 'name' => '江西省'),  2 => array('id' => 2, 'pid' => 0, 'name' => '黑龙江省'),  3 => array('id' => 3, 'pid' => 1, 'name' => '南昌市'),  4 => array('id' => 4, 'pid' => 2, 'name' => '哈尔滨市'),  5 => array('id' => 5, 'pid' => 2, 'name' => '鸡西市'),  6 => array('id' => 6, 'pid' => 4, 'name' => '香坊区'),  7 => array('id' => 7, 'pid' => 4, 'name' => '南岗区'),  8 => array('id' => 8, 'pid' => 6, 'name' => '和兴路'),  9 => array('id' => 9, 'pid' => 7, 'name' => '西大直街'),  10 => array('id' => 10, 'pid' => 8, 'name' => '东北林业大学'),  11 => array('id' => 11, 'pid' => 9, 'name' => '哈尔滨工业大学'),  12 => array('id' => 12, 'pid' => 8, 'name' => '哈尔滨师范大学'),  13 => array('id' => 13, 'pid' => 1, 'name' => '赣州市'),  14 => array('id' => 14, 'pid' => 13, 'name' => '赣县'),  15 => array('id' => 15, 'pid' => 13, 'name' => '于都县'),  16 => array('id' => 16, 'pid' => 14, 'name' => '茅店镇'),  17 => array('id' => 17, 'pid' => 14, 'name' => '大田乡'),  18 => array('id' => 18, 'pid' => 16, 'name' => '义源村'),  19 => array('id' => 19, 'pid' => 16, 'name' => '上坝村'),);print_r(genTree5($items));print_r(genTree9($items));//后者输出格式，前者类似，只是数组键值不一样，不过不影响数据结构/*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] => 赣州市            [son] => Array              (                [0] => Array                  (                    [id] => 14                    [pid] => 13                    [name] => 赣县                    [son] => Array                      (                      [0] => Array                        (                          [id] => 16                          [pid] => 14                          [name] => 茅店镇                          [son] => Array                            (                            [0] => Array                              (                              [id] => 18                              [pid] => 16                              [name] => 义源村                              )                             [1] => Array                              (                              [id] => 19                              [pid] => 16                              [name] => 上坝村                              )                             )                         )                       [1] => Array                        (                          [id] => 17                          [pid] => 14                          [name] => 大田乡                        )                       )                   )                 [1] => Array                  (                    [id] => 15                    [pid] => 13                    [name] => 于都县                  )               )           )       )   ) [1] => Array  (    [id] => 2    [pid] => 0    [name] => 黑龙江省    [son] => Array      (        [0] => Array          (            [id] => 4            [pid] => 2            [name] => 哈尔滨市            [son] => Array              (              [0] => Array                (                  [id] => 6                  [pid] => 4                  [name] => 香坊区                  [son] => Array                    (                    [0] => Array                      (                        [id] => 8                        [pid] => 6                        [name] => 和兴路                        [son] => Array                          (                            [0] => Array                              (                              [id] => 10                              [pid] => 8                              [name] =>                               东北林业大学                              )                             [1] => Array                              (                              [id] => 12                              [pid] => 8                              [name] =>                              哈尔滨师范大学                              )                           )                       )                     )                 )               [1] => Array                (                  [id] => 7                  [pid] => 4                  [name] => 南岗区                  [son] => Array                    (                    [0] => Array                      (                      [id] => 9                      [pid] => 7                      [name] => 西大直街                      [son] => Array                        (                        [0] => Array                          (                          [id] => 11                          [pid] => 9                          [name] =>                           哈尔滨工业大学                          )                         )                       )                     )                 )               )           )         [1] => Array          (            [id] => 5            [pid] => 2            [name] => 鸡西市          )       )   ))*/