What is "symfony4"
Symfony, according to official documentation:
It is a set of reusable components written in PHP, a web development framework, a philosophy and a community.
That since version 4.* has brought innovations in its architecture allowing the developer to use from the most basic packages to small applications and fast Apis, such as the possibility to add resources throughout the project transforming it into something complete and robust, maintaining the philosophy of making development as simple as possible.