You should always keep on error reporting, logging of most important events and audit. Otherwise, the day your application will fail for some reason, you'll have a hard time to figure out what happened.
This being said, error reporting must be done internally, and never shown to the end user, since it would be a security issue to show sensitive information. You can use display_errors and log_errors settings for this: in php.ini-production, the first is set to off, while the second is on.
By the way, php.ini-production already answers your question:
; error_reporting
; Default Value: E_ALL & ~E_NOTICE
; Development Value: E_ALL | E_STRICT
; Production Value: E_ALL & ~E_DEPRECATED
Another comment also tells you that:
By default, PHP is set to take action on all errors, notices and warnings EXCEPT
those related to E_NOTICE and E_STRICT, which together cover best practices and
recommended coding standards in PHP. For performance reasons, this is the
recommend error reporting setting. Your production server shouldn't be wasting
resources complaining about best practices and coding standards.