PHP Middleware Pattern: HTTP Request Pipeline

Learn middleware — HTTP pipelines, PSR-15, and building custom middleware.

Core

Middleware = layered processing between request → response.
Each layer can read, modify, or block the request.

Example

class Pipeline {
    private $middlewares = [];

    public function add($mw) {
        $this->middlewares[] = $mw;
    }

    public function handle($request) {
        $handler = fn($req) => "Final Response";

        foreach (array_reverse($this->middlewares) as $mw) {
            $next = $handler;
            $handler = fn($req) => $mw($req, $next);
        }

        return $handler($request);
    }
}

// Middleware
$auth = fn($req, $next) =>
    isset($req['user']) ? $next($req) : "Unauthorized";

$log = fn($req, $next) => (print "Log\n") ? $next($req) : null;

// Usage
$p = new Pipeline();
$p->add($log);
$p->add($auth);

echo $p->handle(['user' => 'admin']);

Real Use Cases

• Authentication / Authorization
• Logging & Monitoring
• Input validation
• Rate limiting
• CORS / headers

Best Practice

• Keep middleware small & single-purpose
• Maintain correct order (auth first)
• Use PSR-15 for interoperability
• Avoid heavy DB logic inside middleware
• Pass data via request attributes