Silex

Spryker is a comprehensive e-commerce platform, providing an alternative solution to building applications with Silex. It's a full-stack solution, potentially making Silex unnecessary for certain projects.

Symfony is a full-stack PHP framework that provides a more comprehensive set of features than Silex. It can be used as an alternative to Silex for building web applications, especially larger and more complex ones. Silex itself is based on Symfony components, and can be considered a microframework form of Symfony

Laravel is a full-stack PHP framework that offers a more complete set of features and a more opinionated structure than Silex. It's a popular alternative for building web applications.

Twig is a templating engine for PHP. It's commonly used with Silex to render dynamic content in web applications.

Composer is a dependency manager for PHP. Silex projects use Composer to manage their dependencies, including Silex itself and other libraries.

Silex is a PHP microframework, therefore PHP is required. It is complementary to Silex.