Making inter-framework system calls

One of the primary reasons for the development of PSR-7 (and middleware) was a growing need to make calls between frameworks. It is of interest to note that the main documentation for PSR-7 is hosted by PHP Framework Interop Group (PHP-FIG).

How to do it...

1. The primary mechanism used in middleware inter-framework calls is to create a driver program that executes framework calls in succession, maintaining a common request and response object. The request and response objects are expected to represent Psr\Http\Message\ServerRequestInterface and Psr\Http\Message\ResponseInterface, respectively.

2. For the purposes of this illustration, we define a middleware session validator. The constants and properties reflect the session thumbprint, which is a term we use to incorporate factors such as the website visitor's IP address, browser, and language settings:

   namespace Application\MiddleWare\Session;
   use InvalidArgumentException;
   use Psr\Http\Message\ { 
     ServerRequestInterface...