What is middleware?
In the realm of web application development Middleware refers to functions wrapped around business logic. They rely upon the decorator pattern and are composed in a sort of layered stack. You could think of them as onion layers, with your business logic residing at the innermost stratum (more on Wikipedia).
Several modern PHP frameworks (such as Zend Expressive and Slim) embrace such framework-agnostic, reuse-oriented paradigm, wholly supporting PSR-7 compliant middleware.
Goal for PHP Middleworld is collecting all available PSR-7 compliant middleware and provide a unique, consistent repository, encouraging middleware reuse and exchange among PHP developers.