i want to know how can make internal live voice calling Application in web site by php not calling to external phone network and not by phone number just by username in site
First you would need a lot more than PHP to make any sort of voice app. Second, I'm sorry but this site isn't a place to have people write code for you, it's to get help with code already written. You might want to look at a freelance programmer but it will probably cost you money. I wish you luck on your endevours.
For this you'd probably need flash and a whole lot more.