如何将Php :: DateInterval转换为秒？

so, I substract two dates:

$d = $start->diff($end);

and now I want to get the date in seconds (not the second parameter). I know it can be done with a native Php function - but it only works above 1970. I know I have to somehow operate with format() method, but I dont get it...

You could access the public properties of the DateInterval class and do some math on it:

$seconds = $d->s + ($d->i * 60) + ($d->h * 3600) + ($d->d * 86400) + ($d->m * 2592000); // and so on

but once we get into the months there will be variance by +/- 2 days unless we stick to an arbitrary definition of a month as 2592000 secs (30 days).

You can also use the difference of the two UNIX timestamps from the DateTime objects (but you will end up having problems with the dates being less than year of 1970):

$seconds = $end->getTimestamp() - $start->getTimestamp();

The following seems to work, although I feel there should be a better way.

$dateIntrvl = $start->diff($end);

$days = $dateIntrvl->format('%a');
$hours = $dateIntrvl->format('%h');
$mins = $dateIntrvl->format('%i');
$secs = $dateIntrvl->format('%s');

$totalSeconds = ($days * 24 * 60 * 60) + ($hours * 60 * 60) + ($mins * 60) + $secs;

And yes, it seems to be working for dates earlier than 1970.