PHP中如何实现数组LRU缓存？

class LRUCache {
    private $capacity;
    private $cache;
    private $order;

    public function __construct($capacity) {
        $this->capacity = $capacity;
        $this->cache = [];
        $this->order = [];
    }

    public function get($key) {
        if (!isset($this->cache[$key])) {
            return -1;
        }

        // 更新访问顺序
        $this->updateOrder($key);
        return $this->cache[$key];
    }

    public function put($key, $value) {
        if (isset($this->cache[$key])) {
            // 如果键已存在，更新值并调整顺序
            $this->cache[$key] = $value;
            $this->updateOrder($key);
        } else {
            // 如果缓存已满，移除最久未使用的元素
            if (count($this->cache) >= $this->capacity) {
                $oldestKey = array_shift($this->order);
                unset($this->cache[$oldestKey]);
            }

            // 添加新元素
            $this->cache[$key] = $value;
            $this->order[] = $key;
        }
    }

    private function updateOrder($key) {
        // 从当前位置移除
        $index = array_search($key, $this->order);
        if ($index !== false) {
            unset($this->order[$index]);
        }

        // 添加到队列头部
        array_unshift($this->order, $key);
    }
}