Does the error "should not be called statically" mean my namespace or use is wrong?

Hi,
I'm confused here. How do I call a method into a controller from another Controller?

PHP Code:

<?php
/**
 * In strict mode, only a variable of exact type of the “type declaration”
 * will be accepted, or a TypeError will be thrown.
 */
declare(strict_types=1);

namespace App\Controllers\Backend;

use App\Controllers\BaseController;
use App\Controllers\Backend\Authentication\Staff;
//use App\Libraries\Auth;


/**
 * The backend starts here.
 */
class Bootstrap extends BaseController
{

 /**
 * Let's get it started. But first, who are you?
 */
 public function index()
 {
 

 // if ( ! $this->authentication->logged('staff'))
 // { 
 Staff::login();
 // }
 // else
 // {
 // $this->dashboard();
 // }
 }
} 


I thought that once I declare the line

Code:

use App\Controllers\Backend\Authentication\Staff;

I should be able to call any method from that class with

Code:

Staff::method_name();

However, that doesn't work and I'm getting the error:

Code:

Non-static method App\Controllers\Backend\Authentication\Staff::login() should not be called statically

What am I missing?
Thanks

>  Does the error "should not be called statically" mean my namespace or use is wrong?

No.
You need to know the difference between static calls and non static calls.
https://www.php.net/manual/en/language.oop5.basic.php

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What am I missing?

You are calling non-static method like static. 
Can you show your Staff class?

Look here if you use Laravel : Facades

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