Symfony

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.
Goal.
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.
Technical.
Symfony was heavily inspired by the Spring Framework.
It makes heavy use of existing PHP open-source projects as part of the framework, including:
Symfony also makes use of its own components, which are freely available on the Symfony Components site for various other projects:
Sponsors.
Symfony is sponsored by SensioLabs, a French software developer and professional services provider. The first name was Sensio Framework, and all classes were therefore prefixed with sf. Later on when it was decided to launch it as open-source framework, the brainstorming resulted in the name symfony (being renamed to Symfony from version 2 and on), which matches the existing theme and class name prefixes.
Real-world usage.
Symfony's own website has a comprehensive list of projects using Symfony and a showcase of websites built with Symfony.
Releases.
Symfony manages its releases through a time-based model; a new Symfony release comes out every six months: one in May and one in November. This release process has been adopted as of Symfony 2.2, and all the "rules" explained in this document must be strictly followed as of Symfony 2.4.
The standard version of Symfony is maintained for eight months, whereas long-term support (LTS) versions are supported for three years. A new LTS release is published biennially.
The current LTS release is version 4.4 as per https://symfony.com/releases/4.4