Is it possible to modify an incoming request's header?

I have a laravel php framework set up, I want to set some header to all incoming requests so my framework's plugin can find it in the header.

Is it possible to modify incoming request's header?

I tried this but it didn't modify the request header.

$_SERVER['HTTP_AUTHORIZATION'] = "Bearer xxx";
echo Request::header("Authorization"); // "" (ie., it displays nothing)

via Chebli Mohamed