I'm having trouble too. Getting error messages that the required files are not being found. I put the FirePHPCore folder as specified in the instructions, but can't get it to work using MAMP and local server.
Switched to XAMPP, did everything the same and it works fine. So OK, maybe some quirk of MAMP.
Then I tried uploading to my web hosting account, installed identically (www/FirePHPCore/), but it does not work, still can't find the required files. Just like the MAMP problem.
I'm guessing this is some sort of PHP problem with my include path. Any experts wanna give advice?
Thanks,
Louis