The SitePoint PHP blog has a new tutorial posted hoping to demystify some of the confusion around HTTP and PSR-7, a standard from the PHP-FIG group around the handling of request and response messages in PHP applications.

The PHP Framework Interoperability Group (PHP-FIG) has relatively recently approved another proposal, the PSR-7: HTTP Messages Interface. The document crystallizes HTTP messages into 7 interfaces which a PHP library should implement if they subscribe to the specification. In PSR-7 By Example, Matthew Weier O’Phinney, editor of the PSR, gives an interesting overview of the specification. So what is it?

They start with the HTTP side of things, briefly covering what HTTP messages are and the format they're transmitted in. Using some example curl requests they show requests and responses involving normal responses, redirects and how they're broken down into objects implementing the MessageInterface, RequestInterface and ResponseInterface. They outline the PSR-7 specification in a UML diagram and talk about some of the challenges associated with PSR-7's handling (including the use of immutable objects and how it fits in with middleware handling).

The post ends with a listing of a few of the frameworks/libraries that already make use of the PSR-7 structure including Symfony, Slim, Guzzle and the HTTPlug client.