Php 在某些日子里从公历转换成波斯历是错误的

我想在代码中使用PHP的IntlDateFormatter来使用波斯日历。 这几天PHP有内置函数，支持波斯日历，工作正常，但我在某些日子遇到了问题

例如，使用此代码，所有日期从格里高利转换为波斯语，直到2018-3-17转换为“1396-12-26”，之后，2018-3-18转换为“1397-12-27”，我不知道为什么年份会增加

我的php代码：

class MyDateTime extends \DateTime {
            protected $calendar='gregorian';
            protected $timezone;
            public function __construct() {     
                $timezone = new \DateTimeZone('Asia/Tehran');
                $this->timezone = $timezone;
                parent::__construct(null, $timezone);
                $this->setCalendar('gregorian');
                $this->modify('2018-2-19');
            }   
            public function setCalendar($calendar) {
                $this->calendar = strtolower($calendar);
                return $this;
            }   
            public function format($pattern){
                $formater = new \IntlDateFormatter('en_US' . '@calendar=' . $this->calendar,
                        \IntlDateFormatter::FULL,  \IntlDateFormatter::FULL, $this->timezone,
                        $this->calendar == 'gregorian' ? \IntlDateFormatter::GREGORIAN : \IntlDateFormatter::TRADITIONAL, $pattern);
                return $formater->format(parent::format('U'));

            }   
        }
        $d = new MyDateTime();
        $d->setCalendar('gregorian');
        echo $d->format('Y-M-d');
         $d->setCalendar('persian');
        echo " Persian: ".$d->format('Y-M-d')."<br >\n";

        echo 'Next mpnth:'." <br>\n";
        $d->modify('+26 day');

        $d->setCalendar('gregorian');
        echo $d->format('Y-M-d');
        $d->setCalendar('persian');
        echo " Persian: ".$d->format('Y-M-d')."<br >\n";            

        echo 'Next day:'." <br>\n";
        $d->modify('+1 day');

        $d->setCalendar('gregorian');
        echo $d->format('Y-M-d');
        $d->setCalendar('persian');
        echo " Persian: ".$d->format('Y-M-d')."<br >\n";

---

不知道为什么你的代码不起作用。旧的PHP版本？这在PHP 7.2.21中可以很好地工作：

function dateGregorianToPersian($strDate)
{
  $tz = new DateTimeZone('Asia/Tehran');
  $fmt = datefmt_create(
    "ir_IR@calendar=persian", 
    IntlDateFormatter::FULL, 
    IntlDateFormatter::FULL, 
    $tz, 
    IntlDateFormatter::TRADITIONAL,
    "yyyy-MM-dd"
  );
  return datefmt_format( $fmt ,date_create($strDate,$tz));
}

//test
$data = ['2018-2-19','2018-3-17','2018-3-18'];
foreach($data as $strDate){
  echo $strDate.' Persian: '.dateGregorianToPersian($strDate).'<br>';
}

---

谢谢你的回复，你也测试过我的代码吗？在公历和波斯历之间切换时，它可能会累积？

function dateGregorianToPersian($strDate)
{
  $tz = new DateTimeZone('Asia/Tehran');
  $fmt = datefmt_create(
    "ir_IR@calendar=persian", 
    IntlDateFormatter::FULL, 
    IntlDateFormatter::FULL, 
    $tz, 
    IntlDateFormatter::TRADITIONAL,
    "yyyy-MM-dd"
  );
  return datefmt_format( $fmt ,date_create($strDate,$tz));
}

//test
$data = ['2018-2-19','2018-3-17','2018-3-18'];
foreach($data as $strDate){
  echo $strDate.' Persian: '.dateGregorianToPersian($strDate).'<br>';
}

2018-2-19 Persian: 1396-11-30
2018-3-17 Persian: 1396-12-26
2018-3-18 Persian: 1396-12-27