所以，解决方法很简单.每个API控制器都扩展了ApiController类的带体：

<?php
namespace App\Controller\Api;

use Cake\Controller\Controller;
use Cake\Event\EventInterface;

class ApiController extends Controller
{

    /**
     * @inheritDoc
     */
    public function initialize(): void
    {
        parent::initialize();

        $this->loadComponent('RequestHandler');

        $this->viewBuilder()->setClassName('Json');
    }

    /**
     * @inerhitDoc
     */
    public function beforeFilter(EventInterface $event)
    {
        parent::beforeFilter($event);

        $status = true;
        $error = '';

        $this->viewBuilder()->setVars(compact('status', 'error'));
    }

    /**
     * @inerhitDoc
     */
    public function beforeRender(EventInterface $event)
    {
        parent::beforeRender($event);

        $this->viewBuilder()->setVar('_serialize', array_keys($this->viewBuilder()->getVars()));
    }
}

如果我想在某个控制器中更改error或status，我可以这样做：

if ($data->isEmpty()) {
    $this->set([
        'status' => false,
        'error' => __d('api', 'No matching records!'),
    ]);
}