Description:
------------
DateTime fractions of a second are ignored when serialized.

A DateTime cannot be correctly serialized and unserialized.


Test script:
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$floatTime = '1400580590.47359';

$nowtime = \DateTime::createFromFormat('U.u', $floatTime);

echo $nowtime->format('Y-m-d H:i:s.u T')."\r\n";

echo serialize($nowtime)."\r\n";

Expected result:
----------------
2014-05-20 10:09:50.473590 GMT+0000
O:8:"DateTime":3:{s:4:"date";s:19:"2014-05-20 10:09:50.473590";s:13:"timezone_type";i:1;s:8:"timezone";s:6:"+00:00";}

/*

Note: this serialized DateTime includes the fraction, and when it is passed to unserialize(), the fraction is correctly set in the resulting DateTime object.

Therefore unserialize() works, serialize() does not work.

*/

Actual result:
--------------
2014-05-20 10:09:50.473590 GMT+0000
O:8:"DateTime":3:{s:4:"date";s:19:"2014-05-20 10:09:50";s:13:"timezone_type";i:1;s:8:"timezone";s:6:"+00:00";}