Rasmus Lerdorf has a new post to his blog sharing the results of some "investigative hacking" he did to see if making ZeroMQ and libevent work together was difficult. Thankfully, the answer was "not hard at all".
While waiting for a connection in Frankfurt I had a quick look at what it would take to make ZeroMQ and libevent co-exist in PHP and it was actually quite easy. Well, easy after Mikko Koppanen added a way to get the underlying socket fd from the ZeroMQ PHP extension. To get this working, install the PHP ZeroMQ extension and the PHP libevent extension.
He includes a sample script show the results of his work, a basic server and client that sends a request to the ZeroMQ server and fires off an event using the libevent library (via PHP's extension. You can find out more about using these two libraries in the PHP manual - libevent and ZeroMQ