How can I create a chat application in PHP?
<p>I'm trying to create a chat system using PHP and javascript. I want to know how the chat in Gmail works: it will remain in the same position even as the user moves to another page. I would be grateful if anyone could explain how it works.</p>

<p>And at the same time, please give some ideas on how to create a chat s/m. For example, the creation of the popup window, protocols to be used with chat, etc.</p>
