[2]Router.php

<?php

namespace Hero;

class Router
{
    private $routes = [];
  
    public function on($method, $path, $callback) 
    { 
        $method = strtolower($method);
        if (!isset($this->routes[$method])) {
            $this->routes[$method] = [];
        }

        $uri = substr($path, 0, 1) !== '/' ? '/' . $path : $path;
        $pattern = str_replace('/', '\/', $uri);
        $route = '/^' . $pattern . '$/';

        $this->routes[$method][$route] = $callback;

        return $this;
    } 
}