Middlware

gistfile1.php

<?php

// Generic middleware that does not have to create a response.
$ringStyle = function(RequestInterface $request, callable $next) {
    $request = $request->withHeader('Foo', 'Bar');
    $response = $next($request);
    $response = $response->withHeader('Baz', 'Bam');
    return $response;
};

// Intercept before calling next.
$intercept = function(RequestInterface $request, callable $next) use ($cache) {
    if ($cache->hasRequest()) {
        return $cache->getResponse($request);
    }
    return $next($request);
};

// $next creates responses. But it's not a middleware.
$next = function(RequestInterface $request) {
    return new Response();
}