Chat on php+ajax for hosting, options?

Question

Chats

Dear passing, calling and ignoring.
Don't be lazy. Minimum knowledge. Hope for you.
We need a simple chat, like the one below, already on the hosting.
Implementation as in the example is not needed.
Let it be php + ajax. Essence: creating rooms, login password, chat.
If anyone has tips, or ready-made small solutions, please share.
Example: Knock

Answer 1

php+ajax will load the server more than node js with sockets. But it's up to you, of course.
Examples:
www.phpfreechat.net
https://github.com/Frug/AJAX-Chat
https://css-tricks.com/chat2/
and others on request in the github "php chat"

Answer 2

The simplest option is to use one of the SaaS comet servers https://habrahabr.ru/company/comet-server/blog/273573/ then the Ajax server will not have to be loaded with requests and will work quickly.
From the developments, I can share the sources of my chat city-chat.comet-server.ru or comet-server.com/wiki/doku.php/comet:star-comet-chat or comet-server.ru/wiki/doku.php/comet :chat-with-auth... could also answer questions on Skype if there are questions about reusing the code of these examples.