title: How to add CarbonInterval instance in Carbon instance
body: <p>I have a carbon instance</p>
  
  <pre><code>   $a = Carbon\Carbon::now();
  
     Carbon\Carbon {
       "date": "2018-06-11 10:00:00",
       "timezone_type": 3,
       "timezone": "Europe/Vienna",
     }
  </code></pre>
  
  <p>and a CarbonInterval instance</p>
  
  <pre><code>   $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,
     }
  </code></pre>
  
  <p>How to add the interval in the carbon instance so that I would get</p>
  
  <pre><code>   Carbon\Carbon {
       "date": "2018-07-11 10:00:00",
       "timezone_type": 3,
       "timezone": "Europe/Vienna",
     }
  </code></pre>
  
  <p>I am aware of solution that involve converting it to timestamp or Datetime class like this </p>
  
  <pre><code>strtotime( date('Y-m-d H:i:s', strtotime("+1 month", $a-&gt;timestamp ) ) );  
  </code></pre>
  
  <p>which is what currently I am using but I am looking for a more "carbony" way I searched through the <a href="https://carbon.nesbot.com/docs/" rel="noreferrer">official site</a> but couldn't find anything on this so need some help.</p>
  
  <p>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 "<code>2</code> <code>days</code>" , "<code>3</code> <code>months</code>" so on that then gets feed to interval classes</p>