How to use old style single pass anonymous function middleware with the PSR-15 spec.

Psr15MiddlewareFromAnonFunc.php

<?php

use Psr\Http\Message\ServerRequestInterface as Request;
use Psr\Http\Message\ResponseInterface as Response;
use Psr\Http\Server\RequestHandlerInterface as Handler;
use Psr\Http\Server\MiddlewareInterface as Middleware;

$middleware = function(Request $req, callable $next): Response {
    $res = $next($req);
    return $res->withHeader('X-Foo', 'Bar');
}

$psr15Middleware = new class ($middeware) implements Middleware {
    private $wrapped;
    public function __construct(callable $mw)
    {
        $this->wrapped = $mw;
    }
    public function process(Request $req, Handler $handler): Response
    {
        return ($this->wrapped)($req, [ $handler, 'handle' ]);
    }
}