Jason R. Briggs at ONLamp.com - LAMP and the Spread Toolkit:
"I don't believe it makes a lot of sense to receive messages in a PHP app (which is not to say in certain circumstances it might not be necessary, just that I'd prefer otherwise). So, from a design perspective in a multi-language environment, while I might send messages from a PHP application, I would potentially look at using Python daemons to handle writing the responses to those messages into a database; perhaps using Ajax polling for live notification to clients, or--the lightest-weight approach--including notifications in a standard page response.
[...] That said, the PHP extension for Spread is, admittedly, not production-ready. There are some stability issues; in particular, if the Spread daemon restarts after the PHP extension has made a connection, a reconnection can cause a persistent crash (not Apache httpd, just the extension itself). Therefore, I would invest in some serious development time with a C-and-PHP guru before relying on the extension for a mission-critical system."