CallbackMiddleware

The CallbackMiddleware is the most minimal middleware provided in PHPNomad. It exists as a utility for injecting arbitrary logic into the request lifecycle without creating a dedicated middleware class.

It’s particularly useful for simple one-off behaviors, rapid prototyping, or cases where full-blown middleware is unnecessary.

Purpose

Middleware normally provides reusable, named behaviors that can be applied across multiple controllers. For example, pagination defaults or record existence checks.

However, sometimes you need lightweight logic that doesn’t justify creating and registering a new class. The CallbackMiddleware makes this possible by letting you pass in any callable and have it run against the request.

This trades formality for flexibility. Use it sparingly, but it can be a good tool for fast iteration.

Contract

CallbackMiddleware implements the standard Middleware interface:

interface Middleware
{
    public function process(Request $request): void;
}

Instead of having its own logic, it simply wraps a user-supplied callable and invokes it during process():

final class CallbackMiddleware implements Middleware
{
    public function __construct(callable $callback) { /* ... */ }

    public function process(Request $request): void
    {
        ($this->callback)($request);
    }
}

The callback receives the normalized request object, allowing you to inspect or modify it before the controller executes.

Example: Adding a Default Parameter

Here’s how you could use CallbackMiddleware to inject a default locale if the request does not already have one:

use PHPNomad\Rest\Middleware\CallbackMiddleware;
use PHPNomad\Http\Interfaces\Request;

$middleware = new CallbackMiddleware(function (Request $request) {
    if (!$request->hasParam('locale')) {
        $request->setParam('locale', 'en_US');
    }
});

When included in a controller’s middleware chain, this ensures every request has a locale parameter available.

Example: Simple Audit Logging

You could also log requests inline without creating a full logger middleware:

use PHPNomad\Rest\Middleware\CallbackMiddleware;
use PHPNomad\Http\Interfaces\Request;

$middleware = new CallbackMiddleware(function (Request $request) {
    error_log("Incoming request to: " . $request->getParam('endpoint'));
});

This is useful for debugging or quick metrics collection.

Best Practices