在开发过程中经常会遇到分级场景,如菜单分级、评论、商品类型分级等;在同一张mysql数据表中可能设计单表结构,如同如下数据:

  $menuList = [
      [ 'id' => 1,'parent_id' => 0, 'name' => '节点1'],
      [ 'id' => 2,'parent_id' => 1, 'name' => '节点1-1'],
      [ 'id' => 3,'parent_id' => 0, 'name' => '节点2'],
      [ 'id' => 4,'parent_id' => 3, 'name' => '节点2-1'],
      [ 'id' => 5,'parent_id' => 2, 'name' => '节点1-1-1'],
      [ 'id' => 6,'parent_id' => 1, 'name' => '节点1-2'],
  ];

这时候在处理展示过程就需要将上面的结构转换为更加直观的数据结构, 形如:

$treeList = [
  [
    children: [
        children: []
    ]
  ]
  [,
    children: [
        children: []
    ]
  ]
];

算法代码如下:

<?php

class Menu
{
    /**
     * 递归循环菜单列表, 转化为菜单树
     * @param $treeList 菜单树列表
     * @param $menuList 菜单列表
     * @return bool
     */
    public function getMenuTree(&$treeList, $menuList)
    {
        // 初始化顶级父节点
        if (! count($treeList)) {
            foreach($menuList as $index => $menu) {
                if ($menu['parent_id'] == 0) {
                    $treeList[] = $menu;
                    unset($menuList[$index]);
                }
            }
        }

        // 递归查找子节点
        foreach ($treeList as &$tree) {
            foreach ($menuList as $index => $menu) {
                if (empty($tree['children'])) {
                    $tree['children'] = [];
                }
                if ($menu['parent_id'] == $tree['id']) {
                    $tree['children'][] = $menu;
                    unset($menuList[$index]);
                }
            }
            if (! empty($tree['children'])) {
                $this->getMenuTree($tree['children'], $menuList);
            } else {
                // 递归临界点
                return false;
            }
        }
    }

}

$menuList = [
  [ 'id' => 1,'parent_id' => 0, 'name' => '节点1'],
  [ 'id' => 2,'parent_id' => 1, 'name' => '节点1-1'],
  [ 'id' => 3,'parent_id' => 0, 'name' => '节点2'],
  [ 'id' => 4,'parent_id' => 3, 'name' => '节点2-1'],
  [ 'id' => 5,'parent_id' => 2, 'name' => '节点1-1-1'],
  [ 'id' => 6,'parent_id' => 1, 'name' => '节点1-2'],
];
$treeList = [];
(new Menu)->getMenuTree($treeList, $menuList);
print_r($treeList);

happy coding!