I want to assign a string value to a global variable inside the controller from database but it displays null

Question

class atmcontroller extends Controller {

    private $uniname;

public function loginvalidation(Request $request){

        $this->validate($request, [
            'username' => 'required',
            'password' => 'required',
        ]);

        $username = $request->input('username');
        $password = $request->input('password');

     $user = DB::table('atmuser')->where('username', '=', $username)->where('password', '=', $password)->get();
     $usercount = $user->count();
     $name = DB::table('atmuser')->where('username', '=' ,$username)->where('password', '=', $password)->pluck('name');

     $this->uniname = (string)$name; **// i want to transfer the value from DB to this->uninmae.**
     
     $balance = DB::table('atmuser')->where('username', '=' ,$username)->where('password', '=', $password)->pluck('balance');

        if (!$usercount == 0) {
            return view('transaction', ['name' => $name , 'balance' => $balance]);
        }
        else {
            return view('login');
        }

    }
}

I want to transfer the value from the DB where it assign to $name to the global variable $this->uniname in order for me to use it as an parameters in if's and else.