I've existing websites with PHP/MySQL framework. They're very busy and chat, occasions, versus (interval) ajax implementations put into server load too. Now websites 're going bigger so I have to switch to lengthy polling/comet but apache is not so well with one of these and the majority of the comet servers are completed in Java. Like cometd, www.stream-hub.com, activemq.
What are the server implementations will be able to use without re-coding the ajax pages in java or least coding in Java/Python.
You might want to have a lookg at Ajax Push Engine its a push engine that work well alongside apache. The server portio is designed in C so its not necessary to bother with managing a java or python server.
Why not consider a SaaS comet solution, for example WebSync On-Demand. You shouldn't have to recode much, you can easily subscribe inside your page, and publish out of your server to that particular customer. Becasue it is a SaaS solution, it really works great with PHP - you will find a pre-built PHP library for precisely what you are attempting to do.