使用函数在PHP中初始化列表

Question

我正在尝试在laravel中添加auth longin功能的特性。请问任何人都可以向我解释: Redirection的含义及其在PHP 7中的作用但不是5.5的原因吗？无论如何要使它在PHP 5.5中运行。谢谢

use Illuminate\Http\RedirectResponse as Redirection;


trait AuthenticatesUsers
{

    public function login(Request $request, Auth $auth) : Redirection
    {
    $authorized = $auth->guard($this->guard)->attempt($request->only('username', 'password'));

        if($authorized){
            return redirect($this->redirectTo);
        }
        return back()->with('authError', 'Login ID or Password is incorrect.')
                 ->withInput($request->except('password'));
    }

}