This is a necessary package, in my opinion.
There are a few things that are needed. I would recommend a prominent link to the Cyrus project in the class-level comment.
I'm unconditional +1 if you add error codes to your use of PEAR::raiseError. In addition, you should not call PEAR::raiseError() directly, but instead bundle it in a method like so:
function raiseError($msg, $code)
($var == null) is true if $var is false or 0, use ($var === null)
Otherwise, very nice, concise, relatively well-documented (could use a little bit more in-depth for a few methods, but this is your prerogative, it is clear enough)