i'm using xampp 1.7.7 in my windows 7 and i can't access PHP application hosted in my PC through LAN in any other computer.
But if i disable Firewall then every thing goes fine; But i dont wanna disable firewall
First of all, firewall on host is blocking your connection. If you are using Windows firewall or any other firewall
So, on computer where is web site hosted go to Control panel-> Windows Firewall and uncheck Don't allow exceptions checkbox. Now open Exceptions tab and click on a button Add program and locate Xampp and Apache. Add them to firewall exception rule.
Maybe you should do this test on some Virtual Machine (VMware, Virtualbox..etc) becouse opening ports and adding exceptions if this machine is connected to Internet is not secure.