Do you mean a commandline thing like -S?

Or do you mean something like this?

  tcp_server("localhost", 9001, function ($addr, $sock) {
    // do stuff here
  });

I meant commandline stuff compared to the newly added php built-in webserer.

How could you determine which script to be executed?
HTTP specify resource to be fetched via URL, but not for general TCP servers.

I don't see how this feature could be useful while users may specify whatever 
server PHP scripts as command line argument.