I want to build a website that only one person at a time can visit. How would I accomplish this task?

I looked at Web counters build in php, but I don't think this is the right solution. Maybe there is an http request?

Thank you in advance.

I want to build a website that only one person at a time can visit. How would I accomplish this task?

I looked at Web counters built in php, but I don't think this is the right solution. Is there an http request for this?

Thank you in advance.