php将sessionid存入mysql

CREATE TABLE `sessions` (
  `id` char(32) NOT NULL,
  `data` text NOT NULL,
  `expiration` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

session_start();

// 连接数据库
$db = new mysqli('localhost', 'username', 'password', 'database_name');

// 检查连接
if ($db->connect_error) {
    die('连接失败: ' . $db->connect_error);
}

// 存储session ID到数据库
if (isset($_COOKIE['PHPSESSID'])) {
    $session_id = $_COOKIE['PHPSESSID'];
    $data = serialize($_SESSION);
    $expiration = time() + ini_get('session.gc_maxlifetime');

    $stmt = $db->prepare("INSERT INTO sessions (id, data, expiration) VALUES (?, ?, ?) ON DUPLICATE KEY UPDATE data = VALUES(data), expiration = VALUES(expiration)");
    $stmt->bind_param('sss', $session_id, $data, $expiration);
    $stmt->execute();
}

// 从数据库读取session数据
$stmt = $db->prepare("SELECT data FROM sessions WHERE id = ? AND expiration > ?");
$stmt->bind_param('si', $session_id, time());
$stmt->execute();
$result = $stmt->get_result();
$row = $result->fetch_assoc();

if ($row) {
    $_SESSION = unserialize($row['data']);
}

// 关闭数据库连接
$db->close();