PHP unix timestamp date format

I really need a good developer for build a PHP function. I have to pass 2 date timestamp to a function(date-begin, date-end) and the function must return a localized date format based on the client. This function also has to understand if the date end is different to the date end, if the dates are equal the function must return the date begin with the time end (if the time end is different to the time start). So, for example if i pass to the function those 2 dates: 20/11/2013 13:00 and 20/11/2013 14:00 (in timestamp), the function must return "20/11/2013 from 13:00 to 14:00". Another example is this one: 20/11/2013 13:00 and 21/11/2013 14:00, the function return "20/11/2013 13:00 to 21/11/2013 14:00". The very important thing is that the function must return the dates formatted correctly based on the vistitator. For example In italy we use this date format d/m/Y H:m, in America they use another date format.