PHP

The way of being a professional coder lays on the path of how proper and reusable the code is. A good developer should always keep the source tidy and understandable. Biggest benefit of this ofcourse time. For example you are always using the same custom functions for accessing a database. So it would be a quicker way if you use a class for handling the database works. A project in a class structure is always reusable because you can slice it into parts for what you need. Otherwise you dig the soup of code for functions. I know many developer don't use classes because of they don't know how powerful the class logic is.