Description:
------------
I'm not sure if this is a problem with the documentation or code.

The documentation states:

> If format does not contain the character ! then portions of the generated time which are not specified in format will be set to the current system time.

When executing the following based on the documentation I'd expect the hour, minute and seconds to be set to the current time however they are set to the epoch.

DateTime::createFromFormat('u', '123456');
// PHP < 7.3: 2019-09-27 14:50:40.123456
// PHP >= 7.3: 2019-09-27 00:00:00.123456

Further investigation led me to discover that the following example also contradicts the documentation and has been the case since the days of PHP 5.3.

DateTimeImmutable::createFromFormat('s', '12');
// 2019-09-27 00:00:12.000000
// Expected (per docs): 2019-09-27 14:50:12.000000

https://3v4l.org/v2bib

I ran a git bisect to identify when the microsecond handling changed which found: 09340ea9b9b2a06c6f1369502806640779073885

Test script:
---------------
<?php

$dt1 = DateTime::createFromFormat('u', '123456');
$dt2 = DateTime::createFromFormat('s', '25');

var_dump($dt1->format('H:i'));
var_dump($dt2->format('H:i:s'));

Expected result:
----------------
string(5) "14:29"
string(8) "14:29:25"

Actual result:
--------------
string(5) "00:00"
string(8) "00:00:25"