Object oriented style
Procedural style
Add a signed amount to a field. Adding a positive amount allows advances in time, even if the numeric value of the field decreases (e.g. when working with years in BC dates).
Other fields may need to adjusted – for instance, adding a month to the 31st of January will result in the 28th (or 29th) of February. Contrary to IntlCalendar::roll(), when a value wraps around, more significant fields may change. For instance, adding a day to the 31st of January will result in the 1st of February, not the 1st of Janurary.
The IntlCalendar resource.
One of the IntlCalendar date/time field constants. These are integer values between 0 and IntlCalendar::FIELD_COUNT.
The signed amount to add to the current field. If the amount is positive, the instant will be moved forward; if it is negative, the instant wil be moved into the past. The unit is implicit to the field type. For instance, hours for IntlCalendar::FIELD_HOUR_OF_DAY.
Returns TRUE on success or FALSE on failure.
<?php
ini_set('intl.default_locale', 'fr_FR');
ini_set('date.timezone', 'UTC');
$cal = new IntlGregorianCalendar(2012, 0 /* January */, 31);
echo IntlDateFormatter::formatObject($cal), "\n";
$cal->add(IntlCalendar::FIELD_MONTH, 1);
echo IntlDateFormatter::formatObject($cal), "\n";
$cal->add(IntlCalendar::FIELD_DAY_OF_MONTH, 1);
echo IntlDateFormatter::formatObject($cal), "\n";
The above example will output:
31 janv. 2012 00:00:00 29 févr. 2012 00:00:00 1 mars 2012 00:00:00
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