today a friend told me that Hunain, did you notice that OOP concepts like inhertance, polymorphism, interface etc aren't usuallt applied to so it made me confused and thought for a while, and yes he seems to be right ! i never used any of them adn even most complex developers never did, among my teachers or friends, is it so ?

is it so ?

No, it is not. If your application is well-designed you'll probably use all of those features.

complexity is a relative term. Is it possible that your teachers/friends are building projects in class that are not embracing these concepts? I've built many simple web apps that do not use all of these concepts. I've been in classes where these concepts are tought, but only tought and not necessarily implemented in a solution.

So I would agree with pritaeas that if your application is well designed for scalability and reuability, some of these components, if not all will be implemented.

commented: great ! +2