Five things you should do (or not do) when you are starting out with PHP.
PHP and MySql are the most common and popular combination you would come across on the Internet. Affordable Linux hosting, open source nature of these two technologies and the freedom from expensive proprietary licenses are the main reasons for the success of this combination.
HTTP is a stateless protocol. That is, a HTTP request to a website has no information or record of the preceding requests. This is where sessions come into picture. Sessions is a mechanism to preserve data across subsequent accesses. Using sessions, a website is able to maintain state, that is, remember which requests they received previously. Without sessions, websites would have not have progressed beyond simple static HTML pages.