$items = array(
            1 => array('id' => 1, 'pid' => 0, 'name' => '安徽省'),
            2 => array('id' => 2, 'pid' => 0, 'name' => '浙江省'),
            3 => array('id' => 3, 'pid' => 1, 'name' => '合肥市'),
            4 => array('id' => 4, 'pid' => 3, 'name' => '长丰县'),
            6 => array('id' => 6, 'pid' => 4, 'name' => '小溪村'),
            5 => array('id' => 5, 'pid' => 1, 'name' => '安庆市'),
        );

 function generateTree($list, $pk = 'id', $pid = 'pid', $child = '_child', $root = 0)
{
    $tree     = array();
    $packData = array();
    foreach ($list as $data) {
        $packData[$data[$pk]] = $data;
    }
    foreach ($packData as $key => $val) {
        if ($val[$pid] == $root) {
//代表跟节点, 重点一
            $tree[] = &$packData[$key];
        } else {
            //找到其父类,重点二
            $packData[$val[$pid]][$child][] = &$packData[$key];
        }
    }
    return $tree;
}

Array ( 
[0] => Array ( [id] => 1 [pid] => 0 [name] => 安徽省 [son] => Array ( [0] => Array ( [id] => 3 [pid] => 1 [name] => 合肥市 [son] => Array ( [0] => Array ( [id] => 4 [pid] => 3 [name] => 长丰县 [son] => Array ( [0] => Array ( [id] => 6 [pid] => 4 [name] => 小溪村 ) ) ) ) ) 
[1] => Array ( [id] => 5 [pid] => 1 [name] => 安庆市 ) ) )

 [1] => Array ( [id] => 2 [pid] => 0 [name] => 浙江省 ) )