routes.php

<?php
/**
 * Routes configuration
 *
 * In this file, you set up routes to your controllers and their actions.
 * Routes are very important mechanism that allows you to freely connect
 * different URLs to chosen controllers and their actions (functions).
 *
 * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
 * Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 *
 * Licensed under The MIT License
 * For full copyright and license information, please see the LICENSE.txt
 * Redistributions of files must retain the above copyright notice.
 *
 * @copyright     Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 * @link          http://cakephp.org CakePHP(tm) Project
 * @license       http://www.opensource.org/licenses/mit-license.php MIT License
 */

use Cake\Core\Plugin;
use Cake\Routing\RouteBuilder;
use Cake\Routing\Router;

/**
 * The default class to use for all routes
 *
 * The following route classes are supplied with CakePHP and are appropriate
 * to set as the default:
 *
 * - Route
 * - InflectedRoute
 * - DashedRoute
 *
 * If no call is made to `Router::defaultRouteClass()`, the class used is
 * `Route` (`Cake\Routing\Route\Route`)
 *
 * Note that `Route` does not do any inflections on URLs which will result in
 * inconsistently cased URLs when used with `:plugin`, `:controller` and
 * `:action` markers.
 *
 */
Router::defaultRouteClass('Route');

// New route we're adding for our tagged action.
// The trailing `*` tells CakePHP that this action has
// passed parameters.
Router::scope(
    '/bookmarks',
    ['controller' => 'Bookmarks'],
    function ($routes) {
        $routes->connect('/tagged/*', ['action' => 'tags']);
    }
);

Router::scope('/', function ($routes) {
    // Connect the default home and /pages/* routes.
    $routes->connect('/', [
        'controller' => 'Pages',
        'action' => 'display', 'home'
    ]);
    $routes->connect('/pages/*', [
        'controller' => 'Pages',
        'action' => 'display'
    ]);

    // Connect the conventions based default routes.
    $routes->fallbacks('InflectedRoute');
    
    // Accept routes using json extension.
    $routes->extensions(['json']);
});

/**
 * Load all plugin routes.  See the Plugin documentation on
 * how to customize the loading of plugin routes.
 */
Plugin::routes();

StudentsController.php

<?php
namespace App\Controller;

use App\Controller\AppController;

/**
 * Students Controller
 *
 * @property \App\Model\Table\StudentsTable $Students
 */
class StudentsController extends AppController
{

    /**
     * Index method
     *
     * @return \Cake\Network\Response|null
     */
    public function index()
    {
        $this->paginate = [
            'contain' => ['Nationalities']
        ];
        $students = $this->paginate($this->Students);

        $this->set(compact('students'));
        $this->set('_serialize', ['students']);
    }

    /**
     * View method
     *
     * @param string|null $id Student id.
     * @return \Cake\Network\Response|null
     * @throws \Cake\Datasource\Exception\RecordNotFoundException When record not found.
     */
    public function view($id = null)
    {
        $student = $this->Students->get($id, [
            'contain' => ['Nationalities']
        ]);

        $this->set('student', $student);
        $this->set('_serialize', ['student']);
    }

    /**
     * Add method
     *
     * @return \Cake\Network\Response|void Redirects on successful add, renders view otherwise.
     */
    public function add()
    {
        $student = $this->Students->newEntity();
        if ($this->request->is('post')) {
            $student = $this->Students->patchEntity($student, $this->request->data);
            if ($this->Students->save($student)) {
                $this->Flash->success(__('The student has been saved.'));
                return $this->redirect(['action' => 'index']);
            } else {
                $this->Flash->error(__('The student could not be saved. Please, try again.'));
            }
        }
        $nationalities = $this->Students->Nationalities->find('list', ['limit' => 200]);
        $this->set(compact('student', 'nationalities'));
        $this->set('_serialize', ['student']);
    }

    /**
     * Edit method
     *
     * @param string|null $id Student id.
     * @return \Cake\Network\Response|void Redirects on successful edit, renders view otherwise.
     * @throws \Cake\Network\Exception\NotFoundException When record not found.
     */
    public function edit($id = null)
    {
        $student = $this->Students->get($id, [
            'contain' => []
        ]);
        if ($this->request->is(['patch', 'post', 'put'])) {
            $student = $this->Students->patchEntity($student, $this->request->data);
            if ($this->Students->save($student)) {
                $this->Flash->success(__('The student has been saved.'));
                return $this->redirect(['action' => 'index']);
            } else {
                $this->Flash->error(__('The student could not be saved. Please, try again.'));
            }
        }
        $nationalities = $this->Students->Nationalities->find('list', ['limit' => 200]);
        $this->set(compact('student', 'nationalities'));
        $this->set('_serialize', ['student']);
    }

    /**
     * Delete method
     *
     * @param string|null $id Student id.
     * @return \Cake\Network\Response|null Redirects to index.
     * @throws \Cake\Datasource\Exception\RecordNotFoundException When record not found.
     */
    public function delete($id = null)
    {
        $this->request->allowMethod(['post', 'delete']);
        $student = $this->Students->get($id);
        if ($this->Students->delete($student)) {
            $this->Flash->success(__('The student has been deleted.'));
        } else {
            $this->Flash->error(__('The student could not be deleted. Please, try again.'));
        }
        return $this->redirect(['action' => 'index']);
    }
}