In the Symfony framework, there is an interesting system of bundle inheritance. It is interesting because it works like object-oriented inheritance, but in reverse. When a bundle is inherited, modifications also affect the parent bundle. This is very convenient: if you don't like a certain component or you want to extend/replace its implementation, you can use the mechanism of bundle inheritance without modifying the parent bundle. However, when using the parent bundle, the new functionality will be used.

OOP in this Ruby of yours is quite different from OOP in our proletarian php =). For example, let's take something as trivial as class fields. Despite the fact that methods are encapsulated, fields are not. (In other words, access modifiers cannot be applied to fields). All fields are protected.

Sometimes a single idea can change everything about programming. For me, one of those ideas was the concept of a service container. It's like the holy grail). Actually, the idea itself is not specific to Symfony framework, it's just one of the successful patterns of application design often used in Symfony.