data = &$data; } public function has($key): bool { return isset($this->data[$key]); } public function get($key) { if (isset($this->data[$key])) { return $this->data[$key]; } return null; } public function set($key, $value): void { $this->data[$key] = $value; } public function delete($key): void { unset($this->data[$key]); } }