get php DateInterval in total 'minutes'

abs((new \DateTime("48 hours"))->getTimestamp() - (new \DateTime)->getTimestamp()) / 60

That's the easiest way to get the difference in minutes between two DateTime instances.

If you are stuck in a position where all you have is the DateInterval, and you (like me) discover that there seems to be no way to get the total minutes, seconds or whatever of the interval, the solution is to create a DateTime at zero time, add the interval to it, and then get the resulting timestamp:

$timeInterval      = //the DateInterval you have;
$intervalInSeconds = (new DateTime())->setTimeStamp(0)->add($timeInterval)->getTimeStamp();
$intervalInMinutes = $intervalInSeconds/60; // and so on