似乎是非常奇怪的要求我看到的一种方式是存储您希望允许在DB中查看内容的电子邮件ID列表，当您的网站被请求时，然后显示一个带有文本的弹出窗口框中要求用户输入电子邮件ID并使用您在DB中存储的电子邮件列表验证电子邮件ID，如果匹配则显示主页，否则重定向到建设网站页面。

It seems to be very strange requirement one way which I see is store the list of email id's which you want to allow to see content in DB and when your web site is requested then show one popup with text box asking email id to enter by user and validate the email id with your stored list of email's in DB if it match then show the home page otherwise redirect to under construction site page.