PHP实现无限级分类

前段时间做一个小项目的时候用到了无限级分类，当时也忘的差不多了，于是就去网上查资料学，下面是我的学习笔记

数据格式:

array (size=5)
  1 =>
    array (size=6)
      'id' => string '1' (length=1)
      'pid' => string '0' (length=1)
      'name' => string '青年之声1' (length=13)
      'description' => string '' (length=0)
      'create_time' => string '2017-04-02 15:38:06' (length=19)
      'del' => string '0' (length=1)
  2 =>
    array (size=6)
      'id' => string '2' (length=1)
      'pid' => string '1' (length=1)
      'name' => string '青年之声2' (length=13)
      'description' => string '' (length=0)
      'create_time' => string '2017-04-02 15:38:06' (length=19)
      'del' => string '0' (length=1)
  3 =>
    array (size=6)
      'id' => string '3' (length=1)
      'pid' => string '2' (length=1)
      'name' => string '青年之声3' (length=13)
      'description' => string '' (length=0)
      'create_time' => string '2017-04-02 15:38:06' (length=19)
      'del' => string '0' (length=1)
  4 =>
    array (size=6)
      'id' => string '4' (length=1)
      'pid' => string '3' (length=1)
      'name' => string '青年之声4' (length=13)
      'description' => string '' (length=0)
      'create_time' => string '2017-04-02 15:38:06' (length=19)
      'del' => string '0' (length=1)
  5 =>
    array (size=6)
      'id' => string '5' (length=1)
      'pid' => string '4' (length=1)
      'name' => string '青年之声5' (length=13)
      'description' => string '' (length=0)
      'create_time' => string '2017-04-02 15:38:06' (length=19)
      'del' => string '0' (length=1)

非递归算法

$tree = array();
foreach ($items as $item) {
	if (isset($items[$item['pid']])) {
		$items[$item['pid']]['childs'][] = &$items[$item['id']];
	} else {
		$tree[] = &$items[$item['id']];
	}
}

递归算法

function getChild($id) {
	$tree = [];
	$childs = Columns::find()->where(['pid' => $id, 'del' => 0])->asArray()->all();
	if ($childs) {
		foreach ($childs as $child) {
			$childTree = getChild($child['id']);
			if ($childTree) {
				$child['children'] = $childTree;
			}
			$tree[] = $child;
		}
	}
	return $tree;
}

最终结果