Error Logging: Handle PHP fatal and non-fatal execution errors

This class can be used to handle PHP fatal and non-fatal execution errors.

It registers an error handler that is capable of a backtrace with the list of functions and arguments used to call the code that causes an error, send that information to the current page output or the PHP error log, or send an e-mail message to the administrator.

The class can also trap fatal errors using a special PHP script shutdown callback function.