PHP and SQL are not reuired to host a site.
In basic terms the way websites tend to work is as follows:
Your browser sends a request to a web server for a file, such as astatalk.com/index.php
The webserver just reads out files to the browser when it recieves these http requests, and this requires a server software like apache.
PHP is a script processor that takes php pages and runs all of the php code in them and outputs the text that is then sent to the browser.
mySQL is a database engine, that php code can connect to get data.

Hopefully this will give a vague understanding of what php and mySQL do, so now to hosting a site:

You can host a site from your own pc by just install apache (or other http server) on it, however there are alot of reasons not to do this, and I wouldn't recommend it at all.
You can get very good free hosting which comes with php and mysql installed on the server, or you can get paid for hosting, which will cost you but as your site grows you will need to get more space etc.
To start with just get a free host, I would recommend 000webhost.com

Hope this helps
tobyb