一个递归函数，用于在PHP中加入至少一个普通用户的帐户

<?php
class User {
    public $id;
    public $name;
    public $children = [];

    public function __construct($id, $name) {
        $this->id = $id;
        $this->name = $name;
    }

    public function addChild(User $child) {
        $this->children[] = $child;
    }
}

function addUsersRecursively(&$users, $parentId = null) {
    foreach ($users as $user) {
        if ($user->id == $parentId) {
            foreach ($users as $childUser) {
                if ($childUser->id != $parentId) {
                    $user->addChild($childUser);
                    addUsersRecursively($users, $childUser->id);
                }
            }
            break;
        }
    }
}

// 创建一些用户
$users = [
    new User(1, 'Admin'),
    new User(2, 'User1'),
    new User(3, 'User2'),
    new User(4, 'SubUser1'),
    new User(5, 'SubUser2')
];

// 添加用户关系
addUsersRecursively($users, 1);

// 打印用户树
function printUserTree(User $user, $indent = '') {
    echo $indent . $user->name . "\n";
    foreach ($user->children as $child) {
        printUserTree($child, $indent . '  ');
    }
}

printUserTree($users[0]);
?>