不用递归实现无限分类数据的树形格式化

　　　　　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();
	} 

9行代码的

    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;
    }

 先取数据后格式化输出

取出的数组格式如下：

    $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'),
	);

from:www.oschina.net/code/snippet_173183_11767

二叉树表设计方式

http://www.phpro.org/tutorials/Managing-Hierarchical-Data-with-PHP-and-MySQL.html