Symfony is a PHP web application framework and a set of reusable PHP components/libraries. It was published as free software on October 18, 2005 and released under the MIT license.
Symfony aims to speed up the creation and maintenance of web applications and to replace repetitive coding tasks. It's also aimed at building robust applications in an enterprise context, and aims to give developers full control over the configuration: from the directory structure to the foreign libraries, almost everything can be customized. To match enterprise development guidelines, Symfony is bundled with additional tools to help developers test, debug and document projects.
Symfony has a low performance overhead used with a bytecode cache.
Symfony was heavily inspired by the Spring Framework.
It makes heavy use of existing PHP open-source projects as part of the framework, including:
Propel or Doctrine as object-relational mapping layers
PDO database abstraction layer (1.1, with Doctrine and Propel 1.3)
PHPUnit, a unit testing framework
Twig, a templating engine
Swift Mailer, an e-mail library
Symfony also makes use of its own components, which are freely available on the Symfony Components site for various other projects:
Symfony YAML, a YAML parser based upon Spyc
Symfony Event Dispatcher
Symfony Dependency Injector, a dependency injector
Symfony Templating, a templating engine