PHP Error Handling: Log fatal and non-fatal PHP errors

This class can log fatal and non-fatal PHP errors.

It registers functions to handle regular errors and a shutdown function to handle fatal errors.

The error handler functions send a message to PHP error log with all the details of the error like the the error source file name, error line number, error message, type of error, time and date of the error.

Optionally the class can also send the error log message by email.