Сommon function in Laravel?

I am puzzled by the following question: if there is a common code for all controllers, for example, method of concrete controller, that detects available language:

public language function(Request $request) {
  $languages = ["en", "it"];
  $default = "en";
  return in_array($request->language, $languages) ? $request->language : $default;
}  

So, some controllers contains this method, that is amiss:

Model::where("Lang", this.language())->get();

Where pull out this method language() avoiding duplication code in each controller? Should it be injected service or simple static class helper?

via Chebli Mohamed