$response->withRedirect() method in slim not rendering global variable for twig created in middleware - slim

Question

<?php
namespace Auto\middleware;
class registrationMiddleware{
public $container;
public function __construct($container){
$this->container=$container;
// $container is the $app instance passed from the route
}
public function __invoke($request,$response,$next){
$this->container->getContainer()->view->getEnvironment()->addGlobal('error','error');
$response=$next($request,$response);
return $response->withRedirect($this->container->getContainer()->get('router')->pathFor('redirect'));
}
}
It does not output global variable (error) on rendering.

Answer 1

It's important to remember that your browser knows nothing about views, and templates, and global variables. All it sees is an HTTP response, which contains a status code, some headers, and optionally a body.
A normal response has a status code of 200, and a body containing the content the browser should display.
The Slim $response->withRedirect method creates an HTTP response with a status code telling the browser to redirect (301, 302, or 307). Although such a response can contain a body, it will generally just be a fallback for browsers that don't automatically redirect. A standard modern browser will never render this content, because as soon as it sees the status code, it will send a new request to the URL given in the response's Location header, and display the content from that to the user instead.
Once the user has been redirected, there is no context left over from before the redirect. The browser has requested a new URL, and your application will receive that new request and process it, with no way of seeing what happened previously. There will be no global variables, views, or anything else, left over from before the redirect. The only information retained will be things you've explicitly saved to cookies, or to the session (which is referenced by a cookie).
The end result of all this being that you cannot both display something with a view and issue an HTTP redirect in the same piece of code.