是否有必要在PHP上包含超类？

I created two classes

teste.php

<?php

namespace Projeto;

use Pai\classepai;
//include 'classepai.php';

class teste extends classePai
{
    public function __construct()
    {
        echo 'classe teste<br>';
    }
}

and

classepai.php

<?php

namespace Pai;


class classepai
{
    public function __construct()
    {
        echo 'classe pai<br>';
    }
}

it returns me an error UNLESS I uncomment include 'classepai.php';

Then I have this class from Laravel (php framework)

<?php

namespace App\Http;

use Illuminate\Foundation\Http\Kernel as HttpKernel;

class Kernel extends HttpKernel
{...}

My question is how can HttpKernel be extended WITHOUT BEING INCLUDED.

HttpKernel is required in composer.json and in code it's included using autoload.php. That's why you don't need to include HttpKernel manually. If you want to do same on classeapi you should add it into composer.json autoload.psr-4 section using namespace and folder location.

Example:

{
    "autoload": {
        "psr-4": {
            "App\\": "app/",
            "Pai\\": "packages/pai/src",
        }
    }
}

Then run command composer dump-autoload and you will be able to use your classeapi like so: Pai\classeapi