Description:
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The DateTime class fails to correctly instantiate with the DATE_RFC3339_EXTENDED when input data is correct.

The example in this bug is taken directly from the documentation at http://php.net/manual/en/class.datetime.php


Test script:
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<?php
$willBeFalse = DateTime::createFromFormat(DATE_RFC3339_EXTENDED, '2005-08-15T15:52:01.000+00:00');

$willAlsoBeFalse = DateTimeImmutable::createFromFormat(DATE_RFC3339_EXTENDED, '2005-08-15T15:52:01.000+00:00');

$date = new DateTime();
$shouldNotBeFalse = DateTime::createFromFormat(DATE_RFC3339_EXTENDED, $date->format(DATE_RFC3339_EXTENDED));

var_dump($shouldNotBeFalse); // false

Expected result:
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The two objects should get instantiated correctly

Actual result:
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$willBeFalse and $willAlsoBeFalse are false