Pablo Viquez has written up a mini-tutorial on getting your Zend Framework application's errors to log out to the Firebug panel (from the extension) with the help of FirePHP and Zend_Log.
I wanted to enable logging of exceptions to my PHP log file and also display them using FireBug. On a standard setup of Zend Framework, the Zend error handler plugin (Zend_Controller_Plugin_ErrorHandler) enable by default [...] I wanted to keep using the error handler plugin and didn't want to log the exceptions by using: Zend_Controller_Front::throwExceptions() or Zend_Controller_Response_Abstract::renderExceptions() or any other way since eventually might get complicated, besides, I think that the error handler plugin works fine and if it gets updated in the future, I won't have to do a major refactor.
He shows how to create the Zend_Log object to write out on the development system (based on the ini setting for the Zend Framework application), how to use it to send the log message out to the waiting client. Examples of the output - a screenshot of the Firebug panel and the error log output.