Laravel - 在控制器功能之间共享变量

I'm new to Laravel and working on a simple project where in my controller (TestController) i have two functions (process & show).

What i'm trying to do is pass $email variable between the functions, so i can use it within the show function, but i don't know how to do that.

Controller

class TestController extends Controller
{    

    public function process(Request $request){
        if($request->ajax()) {
            $email = $request->get( "fullemail" );
        }
    }


    public function show(){

    }

}

Any help would be appreciated. Thanks in advance :)

EDIT

I'm edited my code as followed. Currently i get Too few arguments to function App\Http\Controllers\TestController::show(), 0 passed and exactly 1 expected Error.

Controller

class TestController extends Controller
{    
    public function process(Request $request){
        if($request->ajax()) {
            $email = $request->get( "fullemail" );
            $this->show($email);
        }
    }

    public function show($email){
        dd($email)
    }
}

If you have reached laravel and know what functions are, you probably already know how to do this:

class TestController extends Controller
{    

    public function process(Request $request){
        if($request->ajax()) {
            $email = $request->get( "fullemail" );
            $this->show($email);
        }
    }


    public function show($email){
        // Do whatever you will with the $email variable.
        return view('some.view', ['email' => $email]);
    }

}

An alternative approach:

class TestController extends Controller
{    

    // Declare this variable as a class property - protected means, that only this class and any class that inherits from this class can access the variable.
    protected $email;

    public function process(Request $request){
        if($request->ajax()) {
            $this->email = $request->get( "fullemail" );
            $this->show();
        }
    }


    public function show() {
        // Do whatever you will with the $email variable.
        return view('some.view', ['email' => $this->email]);
        // On top of that, if you change $email value here, the changes will be available in all other methods as well.
        // $this->email = strtolower($this->email);
    }

}