PHP, SSI and CGI are all easy to test on a Windows, MacOS X or Linux PC. First install the web server of your choice, usually either Microsoft Internet Information Server (for Windows XP Professional and all Windows Server operating systems) or Apache (for just about every system there is). Then configure it exactly as you would configure a web server running on a real web host. To test PHP, you'll need to install PHP on your server (MacOS X and Linux users may already have both Apache and PHP installed).
What's going on here? localhost is a special name that always means this computer in front of me that I'm typing on. When you connect to localhost, you're not going out to the Internet, you're talking to your own computer. Most modern PCs are smart enough not to dial out to the Internet just because you are talking to your own computer.
Got a LiveJournal account? Keep up with the latest articles in this FAQ by adding our syndicated feed to your friends list!