unix:// since PHP 3, udg:// since PHP 5
unix:///tmp/mysock
udg:///tmp/mysock
unix:// provides access to a socket stream connection in the Unix domain. udg:// provides an alternate transport to a Unix domain socket using the user datagram protocol.
Unix domain sockets, unlike Internet domain sockets, do not expect
a port number. In the case of fsockopen() the
portno parameter should be set to 0.