I noticed that my_error_handler() is invoked thousands of times during a page execution due to your coding style of referencing unset variables.

You might want to set the new PHP 5 error_types parameter on the call to set_error_handler so at least for those users that run with PHP 5, they won't have the overhead of all those extra calls for E_NOTICE warnings.

I've been mod'ing IPB recently and have made some mistakes of mistyping variable names. It would be nice if you scrubbed the code to avoid the E_NOTICE warnings so those like me that are making changes can turn on E_NOTICE error_reporting and spot our bugs.

Also, it might be nice to have an option to redirect any my_error_handler() messages to a site error file for IPB errors instead of echo'ing them back to the user.

This is not a bug in IPB but is more of a feature suggestion.