Symfony is a full-stack framework, a library of cohesive classes written in PHP. It provides an architecture, components and tools for developers to build complex web applications faster. The Symfony Components are standalone and reusable PHP classes. With no pre-requisite, except for PHP, you can install them today, and start using them right away!
Symphone Components currently consist of YAML, Event Dispatcher & Dependency Injection. YAML is a PHP library that parses YAML strings and converts them to PHP arrays. It can also converts PHP arrays to YAML strings. Event Dispatcher is a PHP library that provides a lightweight implementation of the Observer design pattern. Dependency Injection is a PHP library that provides a robust Dependency Injection Container.
Symfony Components are being developed and maintained by the symfony project team. You can find further information, documentation & download on Symfony Components Website.