请问php网站后台密码怎么修改

// 假设用户已通过身份验证
$userId = $_SESSION['user_id'];

// 获取表单数据
$newPassword = $_POST['new_password'];
$confirmPassword = $_POST['confirm_password'];

// 验证新密码
if ($newPassword !== $confirmPassword) {
    echo "新密码和确认密码不匹配！";
    exit;
}

// 加载用户信息
$user = getUserById($userId);

// 验证旧密码
if (!password_verify($_POST['old_password'], $user['password_hash'])) {
    echo "旧密码错误！";
    exit;
}

// 更新密码
$newPasswordHash = password_hash($newPassword, PASSWORD_DEFAULT);
updateUserPassword($userId, $newPasswordHash);

// 清除会话
session_unset();
session_destroy();

echo "密码修改成功，请重新登录。";