PHP 构造某年的开始时间和结束时间

/**
 * 返回某一年的开始时间和结束时间.
 *
 * @param $year
 * @param string $field
 *
 * @return string
 */
public static function makeYearDate($year, $field = 'from'): string
{
    $from = date('Y-m-d', mktime(0, 0, 0, 1, 1, $year));
    $to = date('Y-m-d', mktime(23, 59, 59, 12, 31, $year));
    if ($field == 'to') {
        return $to;
    }

    return $from;
}