Overview

Expressive allows you to write PSR-7 middleware applications for the web.

PSR-7 is a standard defining HTTP message interfaces; these are the incoming request and outgoing response for your application. By using PSR-7, we ensure that your applications will work in other PSR-7 contexts.

Middleware is any code sitting between a request and a response; it typically analyzes the request to aggregate incoming data, delegates it to another layer to process, and then creates and returns a response. Middleware can and should be relegated only to those tasks, and should be relatively easy to write and maintain.

Middleware is also designed for composability; you should be able to nest middleware and re-use middleware.

With Expressive, you can build PSR-7-based middleware applications:

  • APIs
  • Websites
  • Single Page Applications
  • and more.

Features

Expressive builds on zend-stratigility to provide a robust convenience layer on which to build applications. The features it provides include:

  • Routing

Stratigility provides limited, literal matching only. Expressive allows you to utilize dynamic routing capabilities from a variety of routers, providing much more fine-grained matching capabilities. The routing layer also allows restricting matched routes to specific HTTP methods, and will return "405 Not Allowed" responses with an "Allow" HTTP header containing allowed HTTP methods for invalid requests.

Routing is abstracted in Expressive, allowing the developer to choose the routing library that best fits the project needs. By default, we provide wrappers for Aura.Router, FastRoute, and the zend-mvc router.

  • container-interop

Expressive encourages the use of Dependency Injection, and defines its Application class to compose a container-interop ContainerInterface instance. The container is used to lazy-load middleware, whether it is piped (Stratigility interface) or routed (Expressive).

  • Templating

While Expressive does not assume templating is being used, it provides a templating abstraction. Developers can write middleware that typehints on this abstraction, and assume that the underlying adapter will provide layout support and namespaced template support.

  • Error Handling

Applications should handle errors gracefully, but also handle them differently in development versus production. Expressive provides both basic error handling via Stratigility's own FinalHandler implementation, as well as more advanced error handling via two specialized error handlers: a templated error handler for production, and a Whoops-based error handler for development.