(PHP 5.5.0, PECL >= 3.0.0a1)
IntlCalendar::isSet — Whether a field is set
Returns whether a field is set (as opposed to clear). Set fields take priority over unset fields and their default values when the date/time is being calculated. Fields set later take priority over fields set earlier.
Assuming there are no argument errors, returns
TRUE iif the field is set.
See the example on IntlCalendar::clear().