Of particular note is that this value will be 0 if the statement that caused the error was prepended by the @ error-control operator.
It is important to remember that the standard PHP error handler is completely bypassed. error_reporting() settings will have no effect and your error handler will be called regardless - however you are still able to read the current value of error_reporting() and act appropriately. Of particular note is that this value will be 0 if the statement that caused the error was prepended by the @ error-control operator.