i am working on Server of my LAN. I have build a php application.. i want to make it avail over my network... My server have windows Server 2008 R2... i am using xampp..

When you say "over my network", do you mean over your LAN? Or outside of your LAN? If you just want to be able to get to it on your local network, and assuming it is hosted on port 80, you should be able to just put the name of the machine in your address bar (http://<computer name>:<port>) and get to it. If it doesn't resolve with the computer name try the IP, if that fails still, then you probably need to put an allow rule in your firewall settings for that port.

What have you set up so far? Is the server up and running and xampp installed?

Aside from the information that pixelsoul provided, if you are still unable to connect (via hostname or IP), check to make sure that the server's local firewall isnt enabled and configured in a way that is preventing incoming traffic for that service.

Are you able to access the PHP application if you try from the server itself?

Let us know what you have done to troubleshoot so far.

did you enable access to xampp from the network

check your httpd-xampp.conf file