Add value to field without carrying into more significant fields

# IntlCalendar::roll

(PHP 5 >= 5.5.0, PHP 7, PHP 8, PECL >= 3.0.0a1)

IntlCalendar::roll — Add value to field without carrying into more significant fields

### Description

Object-oriented style

public IntlCalendar::roll(int `$field`, int|bool `$value`): bool

Procedural style

intlcal_roll(IntlCalendar `$calendar`, int `$field`, int|bool `$value`): bool

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.

### Parameters

`calendar`

  An IntlCalendar instance.

`field`

  One of the IntlCalendar date/time field constants. These are integer values between `0` and `IntlCalendar::FIELD_COUNT`.

`value`

  The (signed) amount to add to the field, `true` for rolling up (adding `1`), or `false` for rolling down (subtracting `1`).

### Return Values

Returns `true` on success or `false` on failure.

### Examples

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"`

The above example will output:

    string(20) "01/07/2013, 00:00:00"
    string(20) "01/06/2013, 00:00:00"

### See Also

- IntlCalendar::add() - Add a (signed) amount of time to a field
- IntlCalendar::set() - Set a time field or several common fields at once

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