PHP DateTime createFromFormat不会死于自然死亡

Question

I am confused by the behavior of createFromFormat.

    private function _event_date($eventdate) {

    $this->_logger->err($eventdate);

    $dt = new DateTime();

    $dt->createFromFormat(DATE_ISO8601, $eventdate);

    $formatted = $dt->format("m/d/Y");

    $this->_logger->err($formatted);

    return $formatted;
}

I call _event_date several times. I expect that when I create a new DateTime object, that it will accept the $eventdate and result in a new formatted date.

Strangely enough (to me), my output looks like so:

2013-04-04 15:10:26 UTC error _event_date 2013-04-05T21:00:00-0400
2013-04-04 15:10:26 UTC error _event_date 04/04/2013
2013-04-04 15:10:26 UTC error _event_date 2013-04-12T20:00:00-0400
2013-04-04 15:10:26 UTC error _event_date 04/04/2013
2013-04-04 15:10:26 UTC error _event_date 2013-04-16T18:00:00-0400
2013-04-04 15:10:26 UTC error _event_date 04/04/2013
2013-04-04 15:10:26 UTC error _event_date 2013-04-17T19:30:00-0400
2013-04-04 15:10:26 UTC error _event_date 04/04/2013
2013-04-04 15:10:26 UTC error _event_date 2013-04-18T20:00:00-0400
2013-04-04 15:10:26 UTC error _event_date 04/04/2013

It appears that for some reason, DateTime is holding on to my original $eventdate value.

Why is this? Am I misunderstanding something about how createFromFormat works? Am I missing something about PHP's object model? Did PHP put something in my drink?

-------------- Answer ----------------

Marc B's answer below does fix the issue:

    // month/day/year
private function _event_date($eventdate) {

    $this->_logger->err($eventdate);

    $dt = DateTime::createFromFormat(DATE_ISO8601, $eventdate);

    $formatted = $dt->format("m/d/Y");

    $this->_logger->err($formatted);

    return $formatted;
}

Which yields the correct results:

2013-04-04 15:34:56 UTC error _event_date 2013-04-04T19:30:00-0400
2013-04-04 15:34:56 UTC error _event_date 04/04/2013
2013-04-04 15:34:56 UTC error _event_date 2013-04-05T21:00:00-0400
2013-04-04 15:34:56 UTC error _event_date 04/05/2013
2013-04-04 15:34:56 UTC error _event_date 2013-04-12T20:00:00-0400
2013-04-04 15:34:56 UTC error _event_date 04/12/2013
2013-04-04 15:34:56 UTC error _event_date 2013-04-16T18:00:00-0400
2013-04-04 15:34:56 UTC error _event_date 04/16/2013
2013-04-04 15:34:56 UTC error _event_date 2013-04-17T19:30:00-0400
2013-04-04 15:34:56 UTC error _event_date 04/17/2013
2013-04-04 15:34:56 UTC error _event_date 2013-04-18T20:00:00-0400
2013-04-04 15:34:56 UTC error _event_date 04/18/2013

Answer 1

createFromFormat is a static method, Try

$date = DateTime::createFromFormat(DATE_ISO8601, $eventdate);

instead.

it returns a DateTime object, which you're not capturing, so yes, you're "remembering" the previously set date, which happens to be "now", since you didn't pass in a date as a constructor argument.