PHP
Request/Response cycle
Learn how middlewares chain between request and response.
The request/response cycle
In a middleware chain the request flows from the outside in, the response flows from the inside out. This is the onion model. The outermost middleware starts first, the innermost handler produces the response, then each middleware resumes where it left off.
Each middleware runs its before part before calling $next($request) and its after part after the call. If $next is never called, inner layers never run; this is handy for early returns.
Order matters: an outer middleware runs its before first and its after last, while an inner one is squeezed between the two ends.
Modifying the response
The $next($request) call returns a $response. You can return it as is, or modify it before returning. For example, you can append a header, filter the body, or produce a brand new response.
A common pattern: $response = $next($request); return $response . " [added]";. This automatically marks every response.
In cases like auth you can return a response without calling $next at all; that skips the inner layers.
Exercise Write a response-modifying middleware
Define a responseModifier($request, $next) function. First print echo "before", then take the response of $next($request), print echo "after". Append " [modified]" to the response and return it. The $handler returns "hello". Finally, print the response returned by responseModifier("istek", $handler).
Show example solution
Write function responseModifier($request, $next) { echo "before\n"; $response = $next($request); echo "after\n"; return $response . " [modified]"; }. Then call echo responseModifier("istek", $handler) . "\n";.
Example solution:
<?php
function responseModifier($request, $next) {
echo "before\n";
$response = $next($request);
echo "after\n";
return $response . " [modified]";
}
$handler = function ($request) {
return "hello";
};
echo responseModifier("istek", $handler) . "\n";
Test yourself
-
Match the cycle concepts
- request
- Flows inward
- response
- Flows outward
- $next
- Moves to the next layer
- onion model
- Layered processing
-
What can a middleware do with the response from $next?
- Modify it and return it
- Ignore it and open a new request
- Delete it
- Only log it
Show answer
Modify it and return it — Correct. You can take the response from $next, modify it and return it.
-
Return $response
$response = $next($request);
return ____;
Show answer
$response = $next($request);
return $response;
Next lesson: Middleware chain
