php notify

I'm hopeful this is a solved problem, and I'm just not searching for the right thing yet. I'd like a way to send a 'notify' to php processes that want it, without the use of a moderator or helper process. One way I tried is to use Daniel Rozsnyo multicast patch and have each php process join a multicast group and wait. Interestingly, this works when invoked on the CLI, but not from a browser. Daniel suspects there may be some interference from apache. The basic problem is sort of akin to a chat program. Multiple clients join and sit waiting for new messages. Using ajax, I open an http connection to a php script on the server, which then waits for a certain amount of time for a message. If none arrives, I respond as such and a new connection is created. Otherwise, I send the message back to the client. I need some way to notify the waiting processes that there's a new message so they can spring into action. Thanks! Marty