从PHP DateTime对象获取带小数的纪元时间？

$d = new \DateTime("2016-02-25 19:14:10.080415");

echo floatval($d->getTimestamp() . $d->format(".u")), "
";  // 1456424050.0804

This works, but feels very akward. Is there any better way to get a floating point number of seconds from a DateTime object? I'm looking for the same value that microtime(true) would return for the current time.

Yes, there is an easier way

echo $d->format('U.u');