# IntlCalendar::clear

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

IntlCalendar::clear — Clear a field or all fields

### 说明

面向对象风格

public IntlCalendar::clear(?int `$field` = `null`): true

过程化风格

intlcal_clear(IntlCalendar `$calendar`, ?int `$field` = `null`): true

Clears either all of the fields or a specific field. A cleared field is marked as unset, giving it the lowest priority against overlapping fields or even default values when calculating the time. Additionally, its value is set to `0`, though given the fieldʼs low priority, its value may have been internally set to another value by the time the field has finished been queried.

### 参数

`calendar`

  IntlCalendar 实例。

`field`

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

### 返回值

总是返回 `true`。

### 更新日志

版本 | 说明
--- | ---
8.2.0 | 现在返回类型为 `true`；之前是 bool。

### 示例

示例 #1 IntlCalendar::clear() examples

`<?php
ini_set('intl.default_locale', 'es_ES');
ini_set('date.timezone', 'UTC');
$fields = array(
'FIELD_ERA' => 0,
'FIELD_YEAR' => 1,
'FIELD_MONTH' => 2,
'FIELD_WEEK_OF_YEAR' => 3,
'FIELD_WEEK_OF_MONTH' => 4,
'FIELD_DATE' => 5,
'FIELD_DAY_OF_YEAR' => 6,
'FIELD_DAY_OF_WEEK' => 7,
'FIELD_DAY_OF_WEEK_IN_MONTH' => 8,
'FIELD_AM_PM' => 9,
'FIELD_HOUR' => 10,
'FIELD_HOUR_OF_DAY' => 11,
'FIELD_MINUTE' => 12,
'FIELD_SECOND' => 13,
'FIELD_MILLISECOND' => 14,
'FIELD_ZONE_OFFSET' => 15,
'FIELD_DST_OFFSET' => 16,
'FIELD_YEAR_WOY' => 17,
'FIELD_DOW_LOCAL' => 18,
'FIELD_EXTENDED_YEAR' => 19,
'FIELD_JULIAN_DAY' => 20,
'FIELD_MILLISECONDS_IN_DAY' => 21,
'FIELD_IS_LEAP_MONTH' => 22,
'FIELD_FIELD_COUNT' => 23,
);
function getSetFields(IntlCalendar $cal) {
global $fields;
$ret = array();
foreach ($fields as $name => $value) {
if ($cal->isSet($value)) {
$ret[] = $name;
}
}
return $ret;
}
$cal = new IntlGregorianCalendar(2013, 2 /* March */, 15);
echo "After GregorianCalendar creation\n";
print_r(getSetFields($cal));
echo "\n";
echo IntlDateFormatter::formatObject($cal), "\n";
echo "After the formatter requested the extended year\n";
print_r(getSetFields($cal));
echo "\n";
$cal->clear(IntlCalendar::FIELD_YEAR);
echo "After the year has been cleared, the date stays the same\n";
echo IntlDateFormatter::formatObject($cal), "\n";
echo "because FIELD_EXTENDED_YEAR is still set\n";
print_r(getSetFields($cal));
echo "\n";
var_dump($cal->clear(IntlCalendar::FIELD_EXTENDED_YEAR));
echo "After the extended year has been cleared\n";
print_r(getSetFields($cal));
echo IntlDateFormatter::formatObject($cal), "\n";
echo "\n";
echo "After the fields are recalculated,\n"
. " extended year is set again (to 1970)\n";
print_r(getSetFields($cal));
echo "\n";
$cal->clear();
echo "After calling variant with no arguments\n";
print_r(getSetFields($cal));
echo IntlDateFormatter::formatObject($cal), "\n";`

以上示例会输出：

    After GregorianCalendar creation
    Array
    (
        [0] => FIELD_ERA
        [1] => FIELD_YEAR
        [2] => FIELD_MONTH
        [3] => FIELD_DATE
    )

    15/03/2013 00:00:00
    After the formatter requested the extended year
    Array
    (
        [0] => FIELD_ERA
        [1] => FIELD_YEAR
        [2] => FIELD_MONTH
        [3] => FIELD_DATE
        [4] => FIELD_EXTENDED_YEAR
    )

    After the year has been cleared, the date stays the same
    15/03/2013 00:00:00
    because FIELD_EXTENDED_YEAR is still set
    Array
    (
        [0] => FIELD_ERA
        [1] => FIELD_MONTH
        [2] => FIELD_DATE
        [3] => FIELD_EXTENDED_YEAR
    )

    bool(true)
    After the extended year has been cleared
    Array
    (
        [0] => FIELD_ERA
        [1] => FIELD_MONTH
        [2] => FIELD_DATE
    )
    15/03/1970 00:00:00

    After the fields are recalculated,
     extended year is set again (to 1970)
    Array
    (
        [0] => FIELD_ERA
        [1] => FIELD_MONTH
        [2] => FIELD_DATE
        [3] => FIELD_EXTENDED_YEAR
    )

    After calling variant with no arguments
    Array
    (
    )
    01/01/1970 00:00:00

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