PHP实现多级分类生成树的方法

PHP无限级分类生成树：

/**
 * 生成树
 * @param $items
 * @return array
 */
function generateTree($items){
    $tree = array();
    foreach($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' => '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'),
    5 => array('id' => 5, 'pid' => 1, 'name' => '安庆市'),
);

print_r(generateTree($items));

执行效果：

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
                                        )

                                )

                        )

                    [1] => Array
                        (
                            [id] => 5
                            [pid] => 1
                            [name] => 安庆市
                        )

                )

        )

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

)
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上面生成树的方法可精简为如下代码：

/**
 * 生成树
 * @param $items
 * @return array|mixed
 */
function generateTree2($items) {
  foreach($items as $item)
  $items[$item['pid']]['son'][$item['id']] = &$items[$item['id']];
  return isset($items[0]['son']) ? $items[0]['son'] : array();
}
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原文地址：
https://www.jb51.net/article/65840.htm