In a new post from the Ask About PHP blog they look at handling different types of errors in a popular PHP framework, CodeIgniter, most being included with the framework.

The way I see it, there are 2 types of errors we have to work with. The ones which are displayed out in nice friendly text to your users, and the type which are hidden and shown only to you as the coder to figure out where something has gone wrong. CI provides the means to do both, thankfully.

They look at the error handling the framework provides for the system/application errors that might happen in the normal course of the use of your PHP application and the configuration file settings you can change to customize the level you want to report at.