I'm looking for a (preferably free) software solution that will act like a server (while offline) on my home PC so that I can test php files and other scripts I make, instead of having to upload them elsewhere just to test them.
Thanks in advance.

Easyphp does the job.

Fairly straightforward to set up and a doddle to use.

xampp does it well too.
http://www.apachefriends.org/en/xampp.html

When i was a student I'm using WAMP5. One good thing about this, is that it has PHPmyadmin

Great replies - very helpful!
Thanks very much!

XAMPP all the way!!! I second the suggestion above!

i use xampp too.

but does it really mirror the whole thing when you upload it to your server?

i've done a lot of hacks and mods on my site, and i'm a bit afraid that i would repea those steps if i do set it up on air from local.

I have been using WAMP5, but xampp looks pretty cool too. I'll have to check it out and maybe think about switching over. I don't do a huge amount on my local system though.