Laravel Session Variables and Middleware

Back when I wrote the code to localize this site I ran into some unexpected behavior that I couldn't figure out. I have two ways to set the language here - first you can do it by subdomain, fr defaults to French. Then regardless of the subdomain you can use the drop-down menu in the navbar to set the language, which sets a session variable. To handle the subdomain I have a middleware which runs on every request and sets the locale to the language specified by the subdomain, if a subdomain is used. I was confused by why the subdomain could be overwritten by the session var set with the drop-down menu, but I ended up leaving it that way because it worked better than the way I had originally envisioned.

This weekend I decided to try to get to the bottom of why the behavior was different than what I would have expected and I discovered something a bit bizarre about Laravel sessions. In the middleware the session is always empty, but I can set a variable and access it from within the middleware. By the time I get to the controller the values put in session in the middleware are gone, and replaced with the values previously set in the session. I haven't looked at Laravel's session code yet, but I assume that however it stores session variables is initialized somewhere between the middleware and the controller. Before I started with Laravel, I used to keep session variables in $_SESSION, so the way it works now is a bit confusing to me.

To explain, I have the following in my middleware, which is registered to run on every request:

public function handle($request, Closure $next)
{
  echo "1: " . session('foo') . "
";
  session(['foo' => 'bar']);
  echo "2: " . session('foo') . "
";
  return $next($request);
}

When I load any page, it outputs:

1: 

2: bar

If I then in a controller execute:

session(['foo' => 'baz']);

And load another page which just contains:

echo "3. " . session('foo');

The output, with the middleware is:

1. 

2. bar

3. baz

So, in the middleware you can set and access the session, but the session doesn't persist past the request, and by the time the controller is executed that session has been replaced with a session that does persist from the previous request. I can think of a few ways around this, but it doesn't seem worth the effort involved. For me, the result of this issue is that I have to include a call to a helper function in every single page I want to translate - if I want to keep the drop-down menu to translate. My other option would be to just do the localization based on subdomain and have the drop-down menu link to the same page on a different subdomain instead of just setting a variable and reloading the same page, which may in fact be a better solution, but again maybe not worth the effort.

I don't know if anyone else has run into this behavior in Laravel, I also don't know if this behavior is intentional or not, but if you are trying to access or set session variables in a middleware with no luck this is likely the reason.