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。
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'),);echo ;
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 ) ) ))*/
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