Convert DateTime to String PHP

I have already researched a lot of site on how can I convert PHP DateTime object to String. I always see "String to DateTime" and not "DateTime to String" PHP DateTime can be echoed, but what i want to process my DateTime with PHP string functions. My question is how can I make PHP dateTime Object to a string starting from this kind of code: $dts = new DateTime(); //this returns the current date time echo strlen($dts);