datetime - Get Date difference and add to new date php -

I have two dates and I want to get the difference. I can do strtotime like this

  $ Ts1 = Stratom ($ 1 date); $ Ts2 = Stratom ($ 2 date); $ Sec_diff = $ ts2 - $ ts1;  

I want to add the result to today's date. Like I get results of 1 year and 20 days. My new date will be next year and 20 days. How can I add the result to the new date.Thank you, my problem is not different, but this is how to add a new date.