I am a newbie at web programming. I have basic PHP programming skills.
From what I understand about PHP is, it runs on the server side and generates a HTML code, server-side PHP script ends, and then that generated HTML code is sent to us (us = browsers of the clients). But in some webpages (programmed with PHP) which I encounter on the internet, the server-client interaction keeps running silently at the background even a long time after the page had completed loading.
For example, in the Stack Exchange communities, when I am viewing new questions I see that the vote counts are changing (as other users vote) without refreshing the page. This indicates that a background script is communicating with a database, right?
Are these kind of pages implemented by pure PHP?
If yes, I thought PHP script had to finish at the server side before the generated HTML code to be sent. What is the secret of this method?
If no, what additional programming languages and/or web technologies do I have to study to learn it? Do they combine another technologies with PHP?
Please guide me on this.
You are asking about means to an end (how to make pages dynamic) when is seems what you need to know about is an end (dynamic pages).
You are basically correct about how PHP works.
However, you overlooked a thing about how webpages work: for the server to send anything, a webpage for instance, there must be request from the client. Therefore, it would be more appropriate to ask how the server can do this without a request from the client.
To answer some of your questions:
Are these kind of pages implemented by pure PHP? –> No it isn’t.
If no, what additional programming languages and/or web technologies do I have to study to learn it? –> Rather than particular PLs or technologies it would be wiser to think in the lines of “How can the server initiate communication with the client (browser/page)?” (or make it appear as though) as this is the “secret” (or more appropriately the key) in implementing such pages. You can find a number of technologies, techniques, and combination of both that deals with this (push technology, long polling, ajax, etc.).
Do they combine another technologies with PHP? –> Yes, as with most stuff on the web, dynamic pages are the combinations of a number of technologies and techniques.
I believe you looked at what you want to accomplish on the wrong angle. Hope this gets you on track!