PHP-FIG standards related to the HTTP Message Interface (PSR-7) have been in place for some time now. The standard for HTTP Handlers (PSR-15) is approved as of Jan 22, 2018.

Laravel already provides a pathway for obtaining PSR-7 request objects from route closures or controller methods. Laravel also allows returning PSR-7 response objects from a route or controller. However, having a new PSR related to middleware doesn't necessarily mean that Laravel needs to implement a compliant middleware stack... nor should it. Using a bridge (like this library) is a perfectly acceptable way to adopt PSR-15 capabilities within Laravel without completely changing the underlying framework.

Middleware is a simple thing and for the most part, middleware should be thin and are easily written. In fact, many are nothing more than single line libraries that could be just as easily created as imported. However, there is some value in re-usable web components that can be shared between applications/frameworks. Many PSR-15 middleware components already exist in the PHP community, some of which can provide some value. Having them available to use in Laravel could be a benefit.

For what benefit may be gained out of re-usable middleware logic, however small... this library was created.

The laravel-psr15-middleware library (a.k.a. Psr15Middleware) is a Laravel compatible middleware that creates a bridge between PSR-7/PSR-15 interfaces and Laravel's middleware stack and Foundation HTTP message objects.

Once installed, you will be able to run compliant PSR-15 middleware in Laravel using this package's integration in the existing Laravel middleware stack.

This library fully implements the PSR-7 (psr/http-message) message object interfaces. The interface is realized through Zend Diactoros concrete implementations of both the Request and Response objects. It also fully implements the newly approved PSR-15 (psr/http-server-middleware) middleware and (psr/http-server-handler) request handler interfaces. This library uses the Symfony PSR-7 Bridge to make the conversions in both directions between Foundation and PSR-7 message objects.

Within your Laravel project folder, install this package using composer. If you are using Laravel 5.5 or later, service provider registration will happen automatically.

composer require jshannon63/laravel-psr15-middleware  

Then use artisan to publish the package's configuration assets

php artisan vendor:publish
  
Which provider or tag's files would you like to publish?:
  [0] Publish files from all providers and tags listed below
  [1] Provider: Fideloper\Proxy\TrustedProxyServiceProvider
  [2] Provider: Illuminate\Mail\MailServiceProvider
  [3] Provider: Illuminate\Notifications\NotificationServiceProvider
  [4] Provider: Illuminate\Pagination\PaginationServiceProvider
  [5] Provider: Jshannon63\Psr15Middleware\Psr15MiddlewareServiceProvider
  [6] Tag: laravel-mail
  [7] Tag: laravel-notifications
  [8] Tag: laravel-pagination
 >
 
 choose the Psr15MiddlewareServiceProvider

That's it! Now you can configure and run your PSR-15 middleware. The default configuration in /config/psr15middleware.php comes with the exampleMiddleware enabled for demonstration purposes. You will need to disable all of the examples and add your own middleware classes as described below.

1. It is NOT necessary to declare PSR-15 middleware in the app/Http/Middleware/Kernel.php file as is normally done. Psr15Middleware will automatically register itself and its middlewares by pushing them onto the Laravel middleware stack.
2. Config entries are arrays and can can contain classnames, callables or objects as shown in the example below. Each entry has two additional parameters which follow the middleware declaration:
   • "prepend" or "append" will determine if your midleware will be placed at the head or tail of the middleware stack.
   • "before", "after" and "terminable" specify the type of middleware. Before middlewares run before the application acts on the request. After middlewares run after the request has been acted on by the application, but before the response has been sent to the browser. Terminable middlewares run after the browser has received the response and are generally used for housekeeping task which require access to the request and/or response objects.
3. Additional sections for aliases ($routeMiddleware) and groups ($middlewareGroups) which closely adhere to the special route middleware groups within the app\Http\Middleware\Kernel.php file.
4. You can add new groups if you like (i.e., custom as shown).
5. Constructor arguments can be passed for middlewares declared as callables or objects within the configuration. All PSR-15 middleware constructors will be treated as variadic functions and therefore will be able to accept any number of arguments to their constructor. Note: These constructor arguments can also be passed as Laravel middleware route parameters. See the Laravel documentation for more on this feature.

<?php

return [
    'middleware' => [
        [\Jshannon63\Psr15Middleware\exampleMiddleware::class, 'append', 'before'],
        [
            function() {
                return new \Jshannon63\Psr15Middleware\exampleMiddleware('Lovin', 'Laravel');
            },
            'prepend',
            'after'
        ],
        [
            (new \Jshannon63\Psr15Middleware\exampleMiddleware('PSR-15','Rocks')),
            'append',
            'after'
        ]
    ],
    'groups' => [
       'web' => [

        ],
        'api' => [
  
        ],
        'custom' => [
  
        ],
    ],
    'aliases' => [
        'psr15' => [
            (new \Jshannon63\Psr15Middleware\exampleMiddleware('Aliased','Middleware')),
            'prepend',
            'after'
        ]
    ]
];

// your namespace here

use Psr\Http\Server\RequestHandlerInterface;
use Psr\Http\Server\MiddlewareInterface;
use Psr\Http\Message\ServerRequestInterface;
use Psr\Http\Message\ResponseInterface;

class exampleMiddleware implements MiddlewareInterface
{
    // Your constructor will be treated as a variadic function
    // and parameters may be passed either as a middleware route
    // parameter or as defined in the /config/psr15middleware.php
    // config file. You can read more about middleware parameters
    // in the Laravel documentation.

    public function __construct()
    {
        // if needed
    }

    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
    {
        // process any request manipulations here before the handler.
        // remember that only "before" middlewares have access to
        // the request object before the application acts on it.
        // the handler will ensure the next middleware will see any
        // changes to the request object.

        $response = $handler->handle($request);

        // response actions go here after the handler provides
        // you with a response object. keep in mind that any
        // "before" middlewares will only have access to a mock
        // response object and any updates will be lost.

        // "terminable" middlewares are run after the response has
        // been sent back to the browser. they will receive the
        // request object passed into this method and will get
        // a copy of the response object from the handler.

        // return the reponse object here.

        return $response;
    }
}

All PSR-15 middleware is encapsulated and managed entirely by the PSR15Middleware subsystem. On boot, Psr15Middleware will bind a wrapper object for each PSR-15 middleware to make it appear native to Laravel. Then the objects will be placed into the Laravel middleware stack according to your configuration parameters. The middlewares themselves will only be instanitated as needed. Laravel will execute the middelwares according to the system priorites and as modified during registration of PSR-15 middlewares by Psr15Middleware.

Also, keep in mind, that since Psr15Middlware operates on PSR-7 message objects, PSR-15 middlewares will not have access to Laravel/Symfony specific properties and methods of the Foundation message objects.

For some PSR-15 middleware to use, take a look at middlewares/psr15middlewares.

If you would like to contribute refer to CONTRIBUTING.md