How to display the data of discounted products on the main page of Opencart?

Question

CMS

The site has a "Special Price" sidebar located in header.tpl (catalog/view/theme/default/template/common/header.tpl). In it, you need to display data only for those products that have a discount.
I try with <?php foreach ($products as $product) { ?> , it says "Invalid argument supplied for foreach()". Looks like the $products array in header.tpl is not defined.
How to display discounted products data in header.tpl ?

Answer 1

To get a list of products, see catalog/model/catalog/product.php
Out of the box in opencart, there is no way to get products only at a discount, so it’s better to add it to the getProducts() method, otherwise you will have to get a list of all products and filter already in the controller - no well.
Well, as already mentioned, the variables for header.tpl are defined in catalog/controller/common/header.php, so there you load the model, get a list of products and pack it into the $this->data array

Answer 2

Look towards
catalog/controller/common/header.php
The variables for the header template are defined there.

Answer 3

Maybe someone will come in handy: (Relevant for version 1)
Between public function index() { and $this->response->setOutput($this->render()); in controller/PAGE_NAME.php
paste:

// Загружаем модели
    $this->load->model('catalog/product');
    $this->load->model('tool/image');

    if (isset($this->request->get['page'])) {
      $page = $this->request->get['page'];
    } else {
      $page = 1;
    }
    
    if (isset($this->request->get['limit'])) {
      $limit = $this->request->get['limit'];
    } else {
      $limit = $this->config->get('config_catalog_limit');
    }

    $data = array(
      'sort'  => 'p.sort_order',
      'order' => 'ASC',
      'start' => ($page - 1) * $limit,
      'limit' => $limit // Количество на странице
      );

    $results = $this->model_catalog_product->getProductSpecials($data);

    $this->data['special_products'] = array();

    foreach ($results as $result) {
      // Получаем изображение
      if ($result['image']) {
        $image = $this->model_tool_image->resize($result['image'], $this->config->get('config_image_product_width'), $this->config->get('config_image_product_height'));
      } else {
        $image = false;
      }
      // Получаем цену
      if (($this->config->get('config_customer_price') && $this->customer->isLogged()) || !$this->config->get('config_customer_price')) {
        $price = $this->currency->format($this->tax->calculate($result['price'], $result['tax_class_id'], $this->config->get('config_tax')));
      } else {
        $price = false;
      }
      // Получаем цену со скидкой
      if ((float)$result['special']) {
        $special = $this->currency->format($this->tax->calculate($result['special'], $result['tax_class_id'], $this->config->get('config_tax')));
      } else {
        $special = false;
      }	
      // Получаем налоги
      if ($this->config->get('config_tax')) {
        $tax = $this->currency->format((float)$result['special'] ? $result['special'] : $result['price']);
      } else {
        $tax = false;
      }				
      // Получаем рэйтинг
      if ($this->config->get('config_review_status')) {
        $rating = (int)$result['rating'];
      } else {
        $rating = false;
      }

      $this->data['special_products'][] = array(
        'product_id'  => $result['product_id'],
        'thumb'       => $image,
        'name'        => $result['name'],
        'description' => utf8_substr(strip_tags(html_entity_decode($result['description'], ENT_QUOTES, 'UTF-8')), 0, 300) . '..',
        'price'       => $price,
        'special'     => $special,
        'tax'         => $tax,
        'rating'      => $result['rating'],
        'reviews'     => sprintf($this->language->get('text_reviews'), (int)$result['reviews']),
        'href'        => $this->url->link('product/product', 'product_id=' . $result['product_id'])
      );
    }

It is desirable to exclude the first 2 lines of code if they are already indicated somewhere on the page.
The output is something like: Page_NAME.tpl

<ul class="jcarousel-skin">
                    <?php foreach ($special_products as $special_product):

                        $price = (!empty($special_product['special'])) ? '<div class="price">'.$special_product['special'].'</div>' : '';

                        if ($special_product['special'] && $special_product['price']){
                            $tag_price = '<div class="tag-price"><span class="price-new">'. $special_product['special'] .'</span><span class="price-old">'. $special_product['price'] .'</span></div>';
                        } else { $tag_price = ''; }
                        
                        $thumbnail = '';
                        if ($special_product['thumb']) {
                            $thumbnail = '<div class="image"><a href="'. $special_product['href'].'"><img src="'. $special_product['thumb'] .'" alt="'. $special_product['name'] .'" /></a></div>';
                        } else {
                            $thumbnail = '';
                        }
                        $name = '<div class="name"><a href="'.$special_product['href'].'">'. $special_product['name'].'</a></div>';

                        /*Item OUTPUT*/
                    echo '<li>'.$tag_price.$thumbnail.'<div class="about">'.$name.$price.'</div></li>';
                    
                    endforeach; ?>
                    </ul>

I took the code from my snippets, if the front is not clear, use var_dump($special_products);