Which server side programming language is better ?

There's no real answer to that. They all have their strong points and their weak points. Currently PHP has a hell of a lot of support. Wordpress sites are built in PHP, a lot of big name hosting companies have PHP pre-installed and PHP is used on most of the websites on the web right now. A few big name websites are currently using Python in their back-end and more will be to come. I think Ruby is probably the big up and coming thing. I think it will at some point surpass PHP as the dominant language. I've learned PHP pretty well and I know Python a bit too. My goal now is to learn Ruby and pretty much use that as my go to language from now on. The only reason I use PHP is because I have hosting with Host Gator and it's easier to use PHP with them. But I'll soon be doing things strictly in Ruby. That's just me. Do some research at the following sites to see which one is useful for what you want to do. http://php.net/ https://www.ruby-lang.org/en/ https://www.python.org/

Python... most websites like Dropbox, Pinterest, and Instagram uses this software.

Companies such as Google, Yahoo!, Disney, Nokia, and IBM all use Python. In fact, among programming languages, Python had the largest year-on-year job demand growth — at 19%.

Thank you all of you . Now i want to know which back-end language is best for learning in treehouse? And which is easy?

Initially, you will probably get the most bang for your buck with PHP for learning and building simple websites and applications. Later on, a lot people end up switching to languages like Python and Ruby. In my opinion, the advantages of Python and Ruby don't come into play until you are an intermediate level developer with a solid understanding of how to structure a website or application and how to manage your time on projects. I don't think it possible to appreciate what a framework like Ruby on Rails offers until you get past the stage of constantly trying to remember syntax and basics tenets of structure. My experience in starting with Ruby on Rails felt like trying to play ice hockey games before I had grasped ice skating.