PHP Routing: Build a Simple Router with URL Parameters

Routing means mapping a request (the URL path and the HTTP method) to the code that should handle it.

Request	Handler
`GET /`	Home page
`GET /products`	Product list
`GET /products/42`	Show product 42
`POST /products`	Create a product

A small router

index.php

PHP

<?php
final class Router
{
    /** @var array<int, array{method: string, regex: string, handler: callable}> */
    private array $routes = [];

    public function add(string $method, string $pattern, callable $handler): void
    {
        // "/products/{id}" becomes the regular expression  #^/products/(?<id>[^/]+)$#
        $regex = "#^" . preg_replace('#\{(\w+)\}#', '(?<$1>[^/]+)', $pattern) . "$#";

        $this->routes[] = ["method" => $method, "regex" => $regex, "handler" => $handler];
    }

    public function dispatch(string $method, string $path): array
    {
        $pathMatched = false;

        foreach ($this->routes as $route) {
            if (preg_match($route["regex"], $path, $matches) !== 1) {
                continue;
            }

            $pathMatched = true;

            if ($route["method"] !== $method) {
                continue;
            }

            $params = array_filter($matches, "is_string", ARRAY_FILTER_USE_KEY);

            return ($route["handler"])($params);
        }

        return $pathMatched
            ? ["status" => 405, "body" => "Method not allowed"]
            : ["status" => 404, "body" => "Not found"];
    }
}

$router = new Router();

$router->add("GET", "/", fn() => ["status" => 200, "body" => "Home"]);
$router->add("GET", "/products/{id}", fn(array $p) => ["status" => 200, "body" => "Product " . (int) $p["id"]]);
$router->add("POST", "/products", fn() => ["status" => 201, "body" => "Created"]);

foreach ([["GET", "/"], ["GET", "/products/42"], ["POST", "/products"], ["DELETE", "/products"], ["GET", "/missing"]] as [$method, $path]) {
    $r = $router->dispatch($method, $path);
    echo "$method $path -> {$r['status']} {$r['body']}\n";
}

Output

OUTPUT

GET / -> 200 Home
GET /products/42 -> 200 Product 42
POST /products -> 201 Created
DELETE /products -> 405 Method not allowed
GET /missing -> 404 Not found

How it works

add() turns a pattern with {name} placeholders into a regular expression with named groups.
dispatch() tests each route. If the path matches but the method does not, it remembers that.
It passes the named parameters to the handler (["id" => "42"]).
No match: 404. A path that exists with another method: 405.

Route parameters are strings from the URL

$p["id"] is the text "42", and it comes from the visitor. Validate it, cast it, and use a placeholder in SQL.

index.php

PHP

<?php
function intParam(array $params, string $name): ?int
{
    $v = filter_var($params[$name] ?? null, FILTER_VALIDATE_INT);

    return ($v === false || $v < 1) ? null : $v;
}

var_dump(intParam(["id" => "42"], "id"));
var_dump(intParam(["id" => "abc"], "id"));
var_dump(intParam(["id" => "-3"], "id"));

Output

OUTPUT

1
2
3

int(42)
NULL
NULL

Route groups and names

Real routers add groups (all routes under /admin need a login), named routes (generate a URL from a name) and middleware (code that runs before or after a handler). The idea is the same as above.

Do not trust the path

Normalise the path before matching (remove a trailing slash, ignore the query string with parse_url(..., PHP_URL_PATH)). Reject paths that contain .. if you ever map them to files.

Use a library when it grows

For a real project, use a tested router: FastRoute (a small, fast package), or the router that comes with Symfony or Laravel. Writing one is a great way to understand them, but production routers handle many edge cases (caching, optional segments, host matching).

terminal

BASH

composer require nikic/fast-route

info

Why this matters in Laravel

Laravel’s Route::get("/products/{id}", ...) is this idea with groups, middleware, model binding and a compiled route cache. The {id} placeholder works the same way.