strtotime($time . '+ 1 hour');

This is probably the most magical thing I’ve ever done PHP. Pass in the date and time (in this case, in a variable), tell it what you want to do with it, and out comes the updated date and time. I needed to add an hour to the time I was working with. Seems simple until you think about transition to the next day. This function takes care of advancing the date to the next day if necessary.