How to add CarbonInterval instance in Carbon instance

Question

I have a carbon instance

   $a = Carbon\Carbon::now();

   Carbon\Carbon {
     "date": "2018-06-11 10:00:00",
     "timezone_type": 3,
     "timezone": "Europe/Vienna",
   }

and a CarbonInterval instance

   $b = CarbonInterval::make('1month');


     Carbon\CarbonInterval {
     "y": 0,
     "m": 1,
     "d": 0,
     "h": 0,
     "i": 0,
     "s": 0,
     "f": 0.0,
     "weekday": 0,
     "weekday_behavior": 0,
     "first_last_day_of": 0,
     "invert": 0,
     "days": false,
     "special_type": 0,
     "special_amount": 0,
     "have_weekday_relative": 0,
     "have_special_relative": 0,
   }

How to add the interval in the carbon instance so that I would get

   Carbon\Carbon {
     "date": "2018-07-11 10:00:00",
     "timezone_type": 3,
     "timezone": "Europe/Vienna",
   }

I am aware of solution that involve converting it to timestamp or Datetime class like this

strtotime( date('Y-m-d H:i:s', strtotime("+1 month", $a->timestamp ) ) );  

which is what currently I am using but I am looking for a more "carbony" way I searched through the official site but couldn't find anything on this so need some help.

Update: Just to give you the context On frontend I have two controls 1st is for interval (days,months,year) 2nd is a text box so depending on the combination I generate strings dynamically like "2 days" , "3 months" so on that then gets feed to interval classes

Answer 1

I'm not aware of a built-in function to add an interval, but what should work is adding the total seconds of an interval to the date:

$date = Carbon::now(); // 2018-06-11 17:54:34
$interval = CarbonInterval::make('1hour');

$laterThisDay = $date->addSeconds($interval->totalSeconds); // 2018-06-11 18:54:34

---

Edit: Found an easier way!

$date = Carbon::now(); // 2018-06-11 17:54:34
$interval = CarbonInterval::make('1hour');

$laterThisDay = $date->add($interval); // 2018-06-11 18:54:34

This works because Carbon is based on DateTime and CarbonInterval is based on DateInterval. See here for method reference.