I've been testing a few PHP scripts on an Apache server with Apache 2.2, the latest version, and a PHPMyadmin.

Currently I'm running MediaWiki and a PHPbb board, with testing content.

I want to prevent access from the outside world, how would I do this??

Currently typing my IP address doesn't actually show any content of the server, nothing actually shows up, or "this document contains no data!" when viewing it in Firefox, so I assume I am relatively safe.

Please can someone help me with this, thanks!

I'm going to assume this is a strictly test system, with no running webpages running...

Just make sure the necisary ports aren't forwarded to your system and/or set your firewall to block them. If there's no domain pointed at your site the odds of it being scene are pretty low too, as somebody would have to be looking at your public IP to find it.

It is a development-only system. Previously people did find it by my IP in the past when it was just blank-content of testing 123.

I'm using it as a testbed before I transfer stuff to another webserver.

Leave MySQL user scope restricted only to localhost and/or 127.0.0.1, always create and use a different mysql user per database/site to avoid using root (if your mysql account is compromised e.g. through the configuration file stored in your web server, the user will not be able to drop all databases).