Improve DateTime Class

Hi internals, what do you think about improving the modification functionality of the DateTime class. I always get a cold shiver, when I write something like this: <?php $date = new DateTime() $date->modify(‘+15 day’); In my opinion it would be nicer if one could write: $date->modify(15, DateTime::INTERVAL_DAY); // for adding 15 days $date->modify(-15, DateTime::INTERVAL_DAY); // for subtracting 15 days Even better would be to have methods like addDays(), addMonths(), etc. This would make it cleaner and more readable. You do not have to do something like this: $date = new DateTime(); $date->modify(getDaysToAddMethod() . " day"); // I am not sure if a '+' sign is needed if the value is positive And it is fully backward compatible. Best regards Christian