The Symfony project has officially announced PSR-7 support in the latest version of the framework. PSR-7 is a recently approved standard by the PHP-FIG to make a more structured HTTP request and response structure (to aid in interoperability).
Less than 2 weeks ago, the PHP community roundly accepted PSR-7, giving PHP a common set of HTTP Message Interfaces. This has huge potential for interoperability and standardization across all of PHP. This is especially true for middleware: functions that hook into the request-response process. In the future, a middleware written around these new interfaces could be used in any framework. [...] Today, a huge number of projects use Symfony's Request and Response classes (via the HttpFoundation component), including Laravel, Drupal 8 and StackPHP.
[...] For that reason, we're thrilled to announce the 0.1 release of the PSR HTTP Message Bridge: a library that can convert Symfony Request and Response objects to PSR-7 compatible objects and back. This means that once there are middleware written for PSR-7, applications using HttpFoundation will be compatible.
The bridge makes it simpler to swap out the HTTP layer by converting the HTTP objects into something other frameworks can use (or so others can be used by Symfony). They provide some examples of how to put it to use, converting objects both to and from the standard Symfony HttpFoundation versions. There's also a quick note about the RequestInterface and ResponseInterface structure that allows you to bridge your own gaps between the PSR-7 friendly components and Symfony.