What is PHP?

Newbie Introduction to the Web

PHP (recursive acronym for "PHP: Hypertext Preprocessor") is a widely-used Open Source general-purpose scripting language that is especially suited for Web development and can be embedded into HTML.

What distinguishes PHP from something like client-side JavaScript is that the code is executed on the server. If you were to have a script on your server, the client would receive the results of running that script, with no way of determining what the underlying code may be. You can even configure your web server to process all your HTML files with PHP, and then there's really no way that users can tell what you have up your sleeve.

The best things in using PHP are that it is extremely simple for a newcomer, but offers many advanced features for a professional programmer.

What can PHP do?
There are three main areas where PHP scripts are used.

1) Server-side scripting. This is the most traditional and main target field for PHP. You need three things to make this work. The PHP parser (CGI or server module), a web server and a web browser. You need to run the web server, with a connected PHP installation. You can access the PHP program output with a web browser, viewing the PHP page through the server. All these can run on your home machine.

2) Command line scripting. You can make a PHP script to run it without any server or browser. You only need the PHP parser to use it this way.

3) Writing desktop applications. PHP is probably not the very best language to create a desktop application with a graphical user interface, but if you know PHP very well, and would like to use some advanced PHP features in your client-side applications you can also use PHP-GTK to write such programs. You also have the ability to write cross-platform applications this way. PHP-GTK is an extension to PHP, not available in the main distribution.

If you look at mywebsiteworkout.com files, they all have .php extension. Through a dialogue window, BlueVoda Website Builder lets you select .html or .php extension. Because of some special operation that I do, I needed to have .php extension so that the host was able to process those files.

So what's this CGI you mentioned a while back?
The Common Gateway Interface (CGI) is a standard for interfacing external applications with information servers, such as HTTP or Web servers.

A plain HTML document that the Web daemon (it's not demon - even though I prefer to call it that) retrieves is static, which means it exists in a constant state: a text file that doesn't change.

A CGI program, on the other hand, is executed in real-time (I guess it means while you are downloading a web page), so that it can output dynamic information. So what you are telling me is that everything changes one way or another and change remains the only constant.