[Proposal] diffInMicroSeconds / diffInFractionalSeconds about carbon

[briannesbitt]

Not what I expected at first:

$micro = 254687;
$first = Carbon::createFromFormat('Y-m-d H:i:s.u', '2014-02-01 03:45:27.'.$micro);
$micro = 254688;
$second = Carbon::createFromFormat('Y-m-d H:i:s.u', '2014-02-01 03:45:27.'.$micro);

$floatFirst = (float)($first->format('U.u'));
$floatSecond = (float)($second->format('U.u'));
var_dump($floatFirst);
var_dump($floatSecond);
var_dump($floatSecond - $floatFirst);

float(1391244327.2547)
float(1391244327.2547)
float(9.5367431640625E-7)

I think it would have to take this approach:

$firstMicro = $first->micro;
$secondMicro = $second->micro;
var_dump($firstMicro);
var_dump($secondMicro);
var_dump($secondMicro - $firstMicro);
var_dump(($secondMicro - $firstMicro)/1000000);

$diff = $second->diffInSeconds($first) + (($secondMicro - $firstMicro)/1000000);
var_dump($diff);

int(254687)
int(254688)
int(1)
float(1.0E-6)
float(1.0E-6)