There are a few ways for PHP developers to test and use their PHP applications/scripts. These ways include:

* Web Hosting (Free or Paid)
* Personal Web Server
* WAMP (recommended for beginners)

Web Hosting Free or Paid

If you don't know how the internet works still i suggest you read up on HTTP, Servers , Apache, FTP and SSH. Although the majority of these things have nothing to do with php a php programmer should have knowledge in all of these topics for he/she will use each one of these processes in their programming lives. A web hosting service is a type of Internet hosting service that allows individuals and organizations to make their own website accessible via the World Wide Web. Web hosts are companies that provide space on a server they own or lease for use by their clients as well as providing Internet connectivity, typically in a data center. Web hosts can also provide data center space and connectivity to the Internet for servers they do not own to be located in their data center, called collocation. anyway my favorite web host is byethost.com they are free , and are relatively easy to use.

Personal Web Servers

If your just starting out , i highly doubt you will be able to accomplish this. but a personal web server is a server you run out of your own house, that you host files on. this server will have to have a few programs, these programs are PHP, Apache, Mysql, FTP, SSH just to name a few. I also recommend running FreeBSD on your web server it is the most secure OS there is really and they were more or less designed to be a web server.

WAMP ( Recommended for Beginners)

What WAMP does is basically installs, configures and runs Apache, PHP and mysql on your windows computer. you simply have to put your php files in the www directory, then go to your web browser and type 

Code:
http://localhost
and this should load your PHP files.
This software can be found here:
Code:
http://www.wampserver.com/en/
These aren't all the ways php developers run their php scripts, but they are the top three most common ways. also it is good to have a syntax highlighter program my favorite is notepad++ it can be found at the following link.
Code:
http://notepad-plus.sourceforge.net/uk/site.htm
here are a few links to get you started at learning about some of the things i recommended.

SSH
Code:
 http://en.wikipedia.org/wiki/Secure_Shell
http://gsw.edu/~oiit/techsupp/ssh.html

Apache
Code:
http://httpd.apache.org/docs/1.3/misc/tutorials.html
FTP
Code:
http://en.wikipedia.org/wiki/File_Transfer_Protocol