Error Using Middleware in SLIM Framework - php

Question

I have been at this for hours now and can not seem to figure out why it's not working. This my first time using SLIM and my first exposure to middleware. I am trying to follow the tutorial listed on the slim website but just can't get to work.
My bootstrap code:
<?php
require '../vendor/autoload.php';
$app = new Slim\Slim();
$app->get('/test', function() {
echo 'Hello, World';
});
$mw = function ($request, $response, $next) {
$response->getBody()->write('BEFORE');
$response = $next($request, $response);
$response->getBody()->write('AFTER');
return $response;
};
$app->add($mw);
$app->run();
When I run just my slim url without the middleware it runs fine. I get Hello, World as the output when I runt http://mysite/test. But when I add the middleware code as listed on the slim site I get the following error:
Catchable fatal error: Argument 1 passed to Slim\Slim::add() must be an instance of Slim\Middleware, instance of Closure given, called in /Applications/XAMPP/xamppfiles/htdocs/project/api/public/index.php on line 22 and defined in /Applications/XAMPP/xamppfiles/htdocs/academy/api/vendor/slim/slim/Slim/Slim.php on line 1267
Am I missing something? Does the middleware require some other setup? The slim documentation is not very helpful when it comes to this. Any help appreciated.

Answer 1

You seem to have installed Slim 2. You are also mixing Slim 2 and Slim 3 syntax. To install Slim 3 issue the following command.
$ composer install slim/slim
Then use code like following:
<?php
require "vendor/autoload.php";
$app = new \Slim\App;
$mw = function ($request, $response, $next) {
$response->getBody()->write("BEFORE");
$response = $next($request, $response);
$response->getBody()->write("AFTER");
return $response;
};
$app->add($mw);
$app->get("/test", function ($request, $response) {
echo "Hello, World";
});
$app->run();