How to get server user?

I've been looking over the output from phpinfo to find a way to portably get the server user name. It is not obvious to me... Can I get that from an $_ENV or $_SERVER value? I have a web base cms system with a file editor and want to test for ownership of the files and directories without having to hard code the server name. I can get file owner ship but if I want to verify it is the server user account, I would do: (pseudo code) $_name = getOwner() if($_name == < portable reference to server user name>) { // proceed } This would be for enhanced access permissions analysis. If a file is being written to by the server user (via php code) it would be helpful to determine that to forstall error message generation. Thanks JK