It would be nice to have an option that allows you to keep a history of FirePHP messages. Currently if you are navigating around a development site the console only shows FirePHP messages from that page and not any of the previous pages.
An example would be if I am testing a form and press submit, the form will be processed, data saved and then it will redirect the user back to a list of submitted data.
During the time from when the submit button is pressed to the time the user is redirected back to the list of submitted data any FirePHP messages will be sent to the bowser but because the form has redirected you back to the list of data those messages will not be displayed.
I have managed get a console log history by closing the Firebug window and then opening it again. Anything during the time the Firebug window is closed to the time you open it again will be recorded.
Perhaps this is a Firebug issue rather than a FirePHP issue?