https://github.com/slimphp/Slim/blob/3.x/Slim/Route.php#L201 отключи если мешает
<?php
use \Psr\Http\Message\ServerRequestInterface as Request;
use \Psr\Http\Message\ResponseInterface as Response;
require '../vendor/autoload.php';
$app = new \Slim\App;
$app->get('/hello/{name}', function (Request $request, Response $response, array $args) {
$name = $args['name'];
$response->getBody()->write("Hello, $name");
return $response;
});
$app->run();
$app->get('/hello/{name}', ...
GET /hello/Vasia
"GET /vasya