Building a Basic PHP Router Without a Framework

A small router maps an HTTP method and exact path to a handler with a safe 404 fallback.

What It Does and When to Use It

Match an exact method and path with a deliberate 404 fallback. Controllers translate HTTP input to operations; domain services implement rules; templates render escaped output.

Requirements, Inputs and Expected Behavior

Confirm the runtime, extension, environment variables, and permissions before running the examples in production. Decode and normalize paths carefully and do not treat unvalidated path strings as filenames.

Example 1: Basic Operation

Match an exact method and path with a deliberate 404 fallback.

<?php
$routes = ['GET /' => static fn () => 'Home', 'GET /health' => static fn () => 'OK'];
 $method = $_SERVER['REQUEST_METHOD'] ?? 'GET';
 $path = parse_url($_SERVER['REQUEST_URI'] ?? '/', PHP_URL_PATH);
 $handler = $routes[$method . ' ' . $path] ?? null;
 http_response_code($handler ? 200 : 404);
 echo $handler ? $handler() : 'Not Found';

Example 2: Behavior and Validation

Restrict dynamic route parameters before using their values.

<?php
$patterns = ['#^/posts/(?P<id>[1-9][0-9]*)$#D'];
 $path = '/posts/17';
 if (preg_match($patterns[0], $path, $matches)) echo (int)$matches['id'];

Practical Example: Application Use

Return a standards-aware method rejection without falling through to a different handler.

<?php
$allowed = ['GET', 'POST'];
 $method = $_SERVER['REQUEST_METHOD'] ?? 'GET';
 if (!in_array($method, $allowed, true)) {
     http_response_code(405);
     header('Allow: GET, POST');
     exit;
 }
 echo 'Method accepted';

Important Behavior and Edge Cases

The second example highlights: Restrict dynamic route parameters before using their values. The practical example adds: Return a standards-aware method rejection without falling through to a different handler.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• A small router maps an HTTP method and exact path to a handler with a safe 404 fallback.
• Return a standards-aware method rejection without falling through to a different handler.
• Treat template names, route parameters and user data as separate trust domains.