Hi there, Symfony is a web based php MVC framework, by MVC we mean Model, View, controller. Some concepts like layer seperation is used, but mainly used for request/response optimisation. Many open source projects like compose, Behat, Doctrine, Drupal and Jhoomla are using Symfony components.

Main advantages of using Symfony:

  1. Gives us resusable classes and code which can be used again and again.
  2. Allows us to follow standards likeL PSR4, Twig
  3. Allows us to use patterns and principles/practices which can be used across various other projects as well.

Drupal does not uses all the symfony componenst only uses some of them, which are:

  1. ClassLoader
  2. DependencyInjection
  3. EventDispatcher
  4. HTTPFoundation
  5. HTTPKernel
  6. Routing
  7. Serializer
  8. Validator
  9. YAML

There are many components present in symfony like: Asset, Browserkit,cache, console, form, ldap,translation, phpunit bridge etc.