example controller view action

view.php

<?php
    public function view($id = null)
    {
        $article = $this->Articles->find('all', [
            'conditions' => ['Articles.id' => $id],
            'contain' => ['Categories', 'Users']
        ])->first();

        if (empty($article)) {
            $article = $this->Articles->find('all', [
                'conditions' => ['Articles.slug' => $id]
            ])->first();
        }

        if (empty($article)) {
            $this->Flash->error(__('The article could not found. Please, try again.'));
            return $this->redirect($this->referer());
        }

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