(PHP 5.5.0, PECL >= 3.0.0a1)
IntlCalendar::roll — Add value to field without carrying into more significant fields
Adds a (signed) amount to a field. The difference with respect to IntlCalendar::add() is that when the field value overflows, it does not carry into more significant fields.
field
One of the IntlCalendar date/time field constants. These are integer
values between 0 and
IntlCalendar::FIELD_COUNT.
amountOrUpOrDown
The (signed) amount to add to the field, TRUE for rolling up (adding
1), or FALSE for rolling down (subtracting
1).
Returns TRUE on success or FALSE on failure.
Example #1 IntlCalendar::roll()
<?php
ini_set('date.timezone', 'Europe/Lisbon');
ini_set('intl.default_locale', 'pt_PT');
$cal = new IntlGregorianCalendar(2013, 5 /* June */, 30);
$cal->add(IntlCalendar::FIELD_DAY_OF_MONTH, 1);
var_dump(IntlDateFormatter::formatObject($cal)); // "01/07/2013, 00:00:00"
$cal->set(2013, 5 /* June */, 30);
$cal->roll(IntlCalendar::FIELD_DAY_OF_MONTH, true); // roll up, same as rolling +1
var_dump(IntlDateFormatter::formatObject($cal)); // "01/06/2013, 00:00:00"
以上例程会输出：
string(20) "01/07/2013, 00:00:00" string(20) "01/06/2013, 00:00:00"