I\'m trying to find an open source PHP calendar that will play nicely with my zend framework application. Ideally, I should be able to display the events on the public site,
I would suggest using a javascript calendar that allows you to feed it data and it will do the rest. I've looked into http://www.bytecyclist.com/projects/jmonthcalendar/ in the past, and it seems to be sufficient.
Basically, feed your data to your view, or to a helper you create, and jmonthcalendar will fill the calendar. I believe it also supports clicking on the date which triggers a function you can define to get/send data to a controller, etc. It has a lot of other features, but I'll let you read those on your own at that url.
Dojo has a calendar widget for editing http://api.dojotoolkit.org/jsdoc/1.3/dijit.form.DateTextBox
Creating a calendar controller is pretty easy: only a couple of hours work.
Sometimes it can take several hours to get a third party calendar widget integrated into your app. I've messed around with this sort of things a few times and regretted it. Most of the time, for simple stuff like this, it is easier to quickly roll your own rather than spend 2 hours hunting for a third party one, a few hours getting it installed and working, another hour figuring out some mysterious bug etc etc....