laravel request is undefined

I am a newbie in Laravel, so everything is under exploration period. I use angular http post to send data over to laravel and in laravel controller i am able to

dd($request)

Request {#40
  #json: ParameterBag {#32
    #parameters: array:4 [
      "GPTour_id" => 1
      "customer_id" => 1
      "status" => "Confirmed"
      "note" => "asdfasdf"
    ]
  }
  #userResolver: Closure {#300
    class: "Illuminate\Auth\AuthServiceProvider"
    this: AuthServiceProvider {#22 …}
    use: array:1 [
      "$app" => Application {#3
        #basePath: "/Users/haophung/Dropbox/server/websites/nglaravelyep/laravel-backend"
        #hasBeenBootstrapped: true
        #booted: true
        #bootingCallbacks: []

However, if i use

$request->input('key')

i got $request is undefined. Please advise!!!

via Hao Phung