<?php $value = getservbyport(137, "udp"); ?>
The same goes for getservbyname()
(PHP 4, PHP 5)
getservbyport — Get Internet service which corresponds to port and protocol
getservbyport() returns the Internet service associated with port for the specified protocol as per /etc/services.
The port number.
protocol is either "tcp" or "udp" (in lowercase).
Returns the Internet service name as a string.