The good example of FirePHP usage in Magento has been introduced by ActiveCodeline in his post Utilize FireBug (and FirePHP) to speed up Magento development early this year. Here I would like to show you another place you can utilize that function in :)
UPDATE: the FirePHP wrapper class now available as a magento extension though tinycarts channel, simply proceed with the following commands under the top directory of your magento instance:
./pear channel-discover tinycarts.github.com./pear install tinycarts/Lib_Tinycarts_Debug
And skip to usage example.
FirePhp wrapper
Create Firephp.php file in lib/Tinycarts/Debug, or checkout(or download) it from github TinycartsLibs.
The static send() method it’s exact copy of acl() function introduced by ActiveCodeline.
Usage
Go into one of your template files like /catalog/product/view.phtml and call this function like:
NOTE: to let it send debug messages you have to uncomment Mage::setIsDeveloperMode(true); in your index.php in development environment ONLY!!!. Next time I’ll tell you how to split environment and do not bother index.php at all ;)
UPDATE: sinse 1.4 release developer mode can be enabled by defining special environment variable MAGE_IS_DEVELOPER_MODE at your development machine, see configure_magento_error_page.