Action.php

<?php
declare(strict_types=1);

namespace Project\Actions;

use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;

/**
 * Class Action
 *
 * @package Projects\Actions
 */
abstract class Action {
    /**
     * @var ServerRequestInterface
     */
    protected $request;

    /**
     * @var ResponseInterface
     */
    protected $response;

    /**
     * @var array|null
     */
    protected $args;

    /**
     * @param  ServerRequestInterface $request
     * @param  ResponseInterface      $response
     * @param  array|null             $args
     *
     * @return ResponseInterface
     */
    public function __invoke(ServerRequestInterface $request, ResponseInterface $response, $args): ResponseInterface {
        $this->request = $request;
        $this->response = $response;
        $this->args = $args;
        return $this->action();
    }

    abstract protected function action(): ResponseInterface;

    /**
     * @param mixed $data
     * @param bool $success
     * @param bool|mixed $error
     * @return ResponseInterface
     */
    protected function respond($data = null, $success = true, $error = false): ResponseInterface
    {
        $payload = [
            'success' => $success,
            'error' => $error,
            'data' => $data,
        ];

        $json = json_encode($payload, JSON_PRETTY_PRINT);
        $this->response->getBody()->write($json);
        return $this->response->withHeader('Content-Type', 'application/json;charset=utf-8');
    }
}

RequestAuthAction.php

<?php
declare(strict_types=1);

namespace Project\Actions\Authentication;

use Project\Actions\Action;
use Project\Services\Authentication\AuthenticationService;
use Psr\Http\Message\ResponseInterface;

/**
 * Class RequestAuthAction
 *
 * @package Projects\Actions\Authentication
 */
class RequestAuthAction extends Action
{
    /**
     * @var AuthenticationService
     */
    private $authenticationService;

    /**
     * RequestAuthAction constructor.
     *
     * @param AuthenticationService $authenticationService
     */
    public function __construct(AuthenticationService $authenticationService)
    {
        $this->authenticationService = $authenticationService;
    }

    /**
     * {@inheritdoc}
     */
    protected function action(): ResponseInterface
    {
        $username = $this->request->getParsedBodyParam('email', null);
        $password = $this->request->getParsedBodyParam('password', null);
        $ipAddress = $this->request->getAttribute('ip_address');

        // do some validation on the data ...
        
        try {
            $this->authenticationService->authenticate($username, $password, $ipAddress);
            return $this->respond(['your' => 'payload']);
        } catch (AuthenticationServiceException $e) {
            return $this->respond(null, false, $e->getMessage());
        }
    }
}