The PEAR::Net_Ident implements Identification Protocol according
to RFC 1413.

The Identification Protocol (a.k.a., "ident", a.k.a., "the Ident
Protocol") provides a means to determine the identity of a user
of a particular TCP connection. Given a TCP port number pair, it
returns a character string which identifies the owner of that
connection on the server's system.

WWW: http://pear.php.net/package/Net_Ident/