The FSM package implements a Finite State Machine. In addition to maintaining state, this FSM also manages a user-defined payload, therefore effectively making the machine a Pushdown Automaton (a finite state machine with memory).
The Log package provides an abstracted logging framework. It includes output handlers for log files, databases, syslog, email, Firebug, and the console. It also provides composite and subject-observer logging mechanisms.
The Net_SMTP package provides an implementation of the SMTP protocol using PEAR's Net_Socket class.
The Perforce Extension for PHP wraps the public Perforce C/++ API, giving PHP developers direct access to Perforce's native client functions.
The Python extension allows the Python interpreter to be embedded inside of PHP, allowing for the instantiate and manipulation of Python objects from within PHP.
The SASL Extension for PHP makes the Cyrus SASL library functions available to PHP. It aims to provide a 1-to-1 wrapper around the SASL library to provide the greatest amount of implementation flexibility. To that end, it is possible to build both a client-side and server-side SASL implementation entirely in PHP.