Carbon PHP add months

I want add Months from a date.
For example this my date 08/04/2019(D-M-Y)
I use the method addMonth() and I get: 08/05/2019(D-M-Y),
Which means carbon added exactly plus one to the value of M.
But in the calendar the date is 06/05/2019 (D-M-Y)...
This is my code:

$date = new Carbon('2019-04-08');
$date->addMonth() 

I want date will be after month like in the calendar.

via Chebli Mohamed