NULL as
      an argument to reset the error handler.
     
    NULL, set_error_handler() and
      set_exception_handler() now return the previous error
      or exception handler, respectively.
     
    depth
      parameter.
     
    timezone argument, and
      IntlCalendar objects for the
      calendar argument. Furthermore, if the time zone
      is omitted and the calendar doesn't specify a time
      zone, PHP's default time zone from
      date_default_timezone_get() is now used instead of the
      default ICU time zone.