Facebook Apps

If you're creating a Facebook App using CI and get unexplained errors, there are a couple settings that you may need to tweak.

Facebook sends your app various parameters in the URL string (e.g. ?fb_sig_in_iframe=1&fb_sig_locale=en_US&...). CI's default configuration chokes on these URLs.

If your app works fine when you view it directly on your server, but you get an error "The URI you submitted has disallowed characters" when viewing your app in Facebook, the problem is the allowed characters doesn’t include “=” and “&”.

Open /application/config/config.php and set $config['permitted_uri_chars'] = '&=a-z 0-9~%.:_-';

If you get a 404 page not found error when viewing your app in Facebook, CI is using Facebook parameters to determine the controller.

Open /application/config/config.php and set $config['uri_protocol'] = "PATH_INFO";

Thanks to this this forum thread for this info: http://codeigniter.com/forums/viewthread/90185/