You will need a client-side application to initiate the 'stream'.
Either an AJAX widget or maybe a Flash Remoting app with AMFPHP.
Whatever it is, it will need to send out http requests at regular
intervals to grab the chat.
Or use one document which is slowly loaded by the webserver, containing the
streaming data. The document (iframe, object, whatever) can be set to
automatically refresh should the document finish loading, thereby restarting
the streaming connection.