signalling inside php

hi when implementing a connection that stays open for a long time ( comet ), how would i implement signalling between php proses(outstanding requests)??

example timeline:

• request 1 start
• request 1 makes action
• request 1 sleeps
• request 2 start
• request 2 makes action
• request 2 notifies request 1 and go's to sleep
• request 1 wakes up and sends the new data
• request 1 sleeps agen

i was wandering if ther was a methode whitch use less(noting?) cpu prosessing