How Does an Internet Server Work?

Components of a Server

A server is a computer that stores websites on its hard drive. It includes the actual server software, which allows other computers to request web pages from it; various "server-side" languages, such as PHP, which add functionality; a program that hosts databases, such as MySQL; and often email server software.

Sending Requests

Every computer that's connected to the Internet is assigned an Internet Protocol (IP) Address, which is a series of numbers. To make those numbers more human-friendly, the Domain Name System (DNS) exists, which assigns domain names (such as Google.com) to a particular IP address (such as 66.102.9.104). Whenever an Internet user types an address into a browser's address bar, the DNS looks up the IP address associated with the domain name and then finds the server associated with the IP. The server then receives the request.

Processing the Request

All web pages will be sent eventually back to the client (the Internet user or the user's computer) in simple hypertext markup language (HTML) format. When the request is for a simple HTML page, the server simply sends that page back. Often, however, the request is more complicated; for example, when the client fills out a contact form or tries to upload an article to a blog.

PHP

PHP is a programming language that exists on the server that, among other things, can process the results of forms a client completes. Let's say a client is trying to send a webmaster a message using a built-in contact form on a web page. The page, written in HTML, can create forms, but it can't really do anything with them. To actually process them, the server uses a PHP file that the HTML file points to. The information on the form is then stored by the PHP file in a set of variables (signified in PHP by a $ symbol) that can be used for whatever purpose is needed. In this case, the message intended for the webmaster could be stored in a variable called "$message," which the PHP file could then send to the webmaster's email address.

SQL

Websites are really all about data. SQL is a language that can create and maintain databases, and MySQL is a popular server-side program for housing and manipulating those databases. To use a popular example, when you write a post for a blogging service such as WordPress, WordPress stores the content of that post inside a giant database filled with all your posts. When you click "Publish," you're really just filling out a form that gets processed by PHP in the same manner as the above example. The only difference is PHP then sticks the information inside a MySQL database on the server. When someone requests the page that holds the post, your post is pulled from the database by PHP and then outputted to HTML--which is the only thing the viewer sees, because the database and the PHP program only exist on the server.

Sending Information Back

The server sends back the resulting HTML web page via the web's main "transfer protocol" called the HyperText Transfer Protocol. That's the "http" at the beginning of every web address.