There are tactical reasons to adopt strong typehint : easy validation, less code, fashionable. Besides, the first typehints blend in effortlessly with the current application : it is as if typehint was already there. Later, it appears that scalar types paved the way to more substantial code refactoring. Classes emerge from the initial scalar types, code congregate around important values, types gets more complex. Finally, systemic typehint arrives. Type hints become systemic when they help tame the class dependency hell, and help us plan for the new code. During the session, we'll cover the various stages of using typehints, with their advantages, and when not to overuse them.