I am going to be setting up a webserver and file server for a client and need to know what would be the best Linux Distro for this, I need the following.

Apache Webserver with PHP, MYSQL, PHPMYADMIN, APACHE
This would hopefully be installed in the Distro as a default install.

Looking also to setup a file share ont he system so 3 seperate offices can all access the system, however it has to be high security as their will be confidential info stored here.
Is it easy to tell the webserver to only allow access to certain IP addresses.

Also any linux apps that would allow me to do daily backups ont he ststem to a secondary HDD and to another PC(Windows) over the internet.

Finally what can anyone suggest would be the ideal system to set this up on, I am talking 2nd hand system possibly.

ANy help would be great.

well any distro is capable of running all of them. Most of the rpm based distros will have rpm packages for them, although, I can't say for sure if they'll distributed with the distro. I myself would recommend getting the sources and compiling them yourself as you don't know if the packages provided are compiled with all the options you'll need. All of the packages you are inquiring about are avaible as source tarballs and I've never had any problems compiling them.

For apache, it's easy to tell it to give access to only certain IPs - you just add allow ips in httpd.conf. I think this is all you need since php will be going through apache. Mysql, you just don't make it available outside your lan.

I can't really answer your backup question, since I just manually use tar to make back ups of directories I want to back up. I run this on bootup, since I'm using a laptop and that gets powered down and up a lot when moving around.

But as for your main question, any mainstream distro will work as a server for you.