ErrorHandlerMiddleware.php

<?php
namespace App\Error\Middleware;

use Cake\Error\Middleware\ErrorHandlerMiddleware as CoreErrorHandlerMiddleware;
use Zend\Diactoros\Response\RedirectResponse;

/**
 * Error handling middleware.
 *
 * Checks for old urls and 301 redirects to corresonding new ones.
 */
class ErrorHandlerMiddleware extends CoreErrorHandlerMiddleware
{
    public function __construct($renderer = null, array $config = [])
    {
        $this->_defaultConfig['exceptions'] = [
            'Cake\Routing\Exception\MissingControllerException',
            'Cake\Controller\Exception\MissingActionException',
        ];

        parent::__construct($renderer, $config);
    }

    public function handleException($exception, $request, $response)
    {
        if (!in_array(get_class($exception), $this->config('exceptions'), true)) {
            return parent::handleException($exception, $request, $response);
        }

        $newUrl = $this->getNewUrl();
      
        if ($newUrl) {
            reuturn new RedirectResponse(
                $newUrl,
                301
            );
        }
        

        return parent::handleException($exception, $request, $response);
    }
    
    protected function getNewUrl()
    {
        // login here to check if new url exists for existing url
    }
}