Filter Products by Category in Opencart

Question

I have a code in Opencart, it randomly displays the products from the store. I would like to modify this code to display the products of a specific category through id or in the best way.

The original code where I believe the modification can be made, is in the controller folder, follows the code:

$data['products'] = array();

$filter_data = array(
    'sort'  => 'p.date_added',
    'order' => 'DESC',
    'start' => 0,
    'limit' => $setting['limit']
);

$results = $this->model_catalog_random->getRandomProducts($filter_data);

I modified the code and put it like this, but it didn’t work:

$data['products'] = array();

$filter_data = array(
    'filter_category_id'  => '63',
    'sort'  => 'p.date_added',
    'order' => 'DESC',
    'start' => 0,
    'limit' => $setting['limit']
);

$results = $this->model_catalog_random->getRandomProducts($filter_data);

Follow all query code:

class ModelCatalogRandom extends Model {

public function getProduct($product_id) {
    if ($this->customer->isLogged()) {
        $customer_group_id = $this->customer->getGroupId();
    } else {
        $customer_group_id = $this->config->get('config_customer_group_id');
    }   

    $query = $this->db->query("SELECT DISTINCT *, pd.name AS name, p.image, m.name AS manufacturer, (SELECT price FROM " . DB_PREFIX . "product_discount pd2 WHERE pd2.product_id = p.product_id AND pd2.customer_group_id = '" . (int)$customer_group_id . "' AND pd2.quantity = '1' AND ((pd2.date_start = '0000-00-00' OR pd2.date_start < NOW()) AND (pd2.date_end = '0000-00-00' OR pd2.date_end > NOW())) ORDER BY pd2.priority ASC, pd2.price ASC LIMIT 1) AS discount, (SELECT price FROM " . DB_PREFIX . "product_special ps WHERE ps.product_id = p.product_id AND ps.customer_group_id = '" . (int)$customer_group_id . "' AND ((ps.date_start = '0000-00-00' OR ps.date_start < NOW()) AND (ps.date_end = '0000-00-00' OR ps.date_end > NOW())) ORDER BY ps.priority ASC, ps.price ASC LIMIT 1) AS special, (SELECT points FROM " . DB_PREFIX . "product_reward pr WHERE pr.product_id = p.product_id AND customer_group_id = '" . (int)$customer_group_id . "') AS reward, (SELECT ss.name FROM " . DB_PREFIX . "stock_status ss WHERE ss.stock_status_id = p.stock_status_id AND ss.language_id = '" . (int)$this->config->get('config_language_id') . "') AS stock_status, (SELECT wcd.unit FROM " . DB_PREFIX . "weight_class_description wcd WHERE p.weight_class_id = wcd.weight_class_id AND wcd.language_id = '" . (int)$this->config->get('config_language_id') . "') AS weight_class, (SELECT lcd.unit FROM " . DB_PREFIX . "length_class_description lcd WHERE p.length_class_id = lcd.length_class_id AND lcd.language_id = '" . (int)$this->config->get('config_language_id') . "') AS length_class, (SELECT AVG(rating) AS total FROM " . DB_PREFIX . "review r1 WHERE r1.product_id = p.product_id AND r1.status = '1' GROUP BY r1.product_id) AS rating, (SELECT COUNT(*) AS total FROM " . DB_PREFIX . "review r2 WHERE r2.product_id = p.product_id AND r2.status = '1' GROUP BY r2.product_id) AS reviews, p.sort_order FROM " . DB_PREFIX . "product p LEFT JOIN " . DB_PREFIX . "product_description pd ON (p.product_id = pd.product_id) LEFT JOIN " . DB_PREFIX . "product_to_store p2s ON (p.product_id = p2s.product_id) LEFT JOIN " . DB_PREFIX . "manufacturer m ON (p.manufacturer_id = m.manufacturer_id) WHERE p.product_id = '" . (int)$product_id . "' AND pd.language_id = '" . (int)$this->config->get('config_language_id') . "' AND p.status = '1' AND p.date_available <= NOW() AND p2s.store_id = '" . (int)$this->config->get('config_store_id') . "'");

    if ($query->num_rows) {
        return array(
            'product_id'       => $query->row['product_id'],
            'name'             => $query->row['name'],
            'description'      => $query->row['description'],
            'meta_description' => $query->row['meta_description'],
            'meta_keyword'     => $query->row['meta_keyword'],
            'tag'              => $query->row['tag'],
            'model'            => $query->row['model'],
            'sku'              => $query->row['sku'],
            'upc'              => $query->row['upc'],
            'ean'              => $query->row['ean'],
            'jan'              => $query->row['jan'],
            'isbn'             => $query->row['isbn'],
            'mpn'              => $query->row['mpn'],
            'location'         => $query->row['location'],
            'quantity'         => $query->row['quantity'],
            'stock_status'     => $query->row['stock_status'],
            'image'            => $query->row['image'],
            'manufacturer_id'  => $query->row['manufacturer_id'],
            'manufacturer'     => $query->row['manufacturer'],
            'price'            => ($query->row['discount'] ? $query->row['discount'] : $query->row['price']),
            'special'          => $query->row['special'],
            'reward'           => $query->row['reward'],
            'points'           => $query->row['points'],
            'tax_class_id'     => $query->row['tax_class_id'],
            'date_available'   => $query->row['date_available'],
            'weight'           => $query->row['weight'],
            'weight_class_id'  => $query->row['weight_class_id'],
            'length'           => $query->row['length'],
            'width'            => $query->row['width'],
            'height'           => $query->row['height'],
            'length_class_id'  => $query->row['length_class_id'],
            'subtract'         => $query->row['subtract'],
            'rating'           => round($query->row['rating']),
            'reviews'          => $query->row['reviews'] ? $query->row['reviews'] : 0,
            'minimum'          => $query->row['minimum'],
            'sort_order'       => $query->row['sort_order'],
            'status'           => $query->row['status'],
            'date_added'       => $query->row['date_added'],
            'date_modified'    => $query->row['date_modified'],
            'viewed'           => $query->row['viewed']
        );
    } else {
        return false;
    }
}

public function getRandomProducts($data = array()) {
    if ($this->customer->isLogged()) {
        $customer_group_id = $this->customer->getGroupId();
    } else {
        $customer_group_id = $this->config->get('config_customer_group_id');
    }   

    $cache = md5(http_build_query($data));

    $product_data = $this->cache->get('product.' . $cache . '.' . $customer_group_id);

    //if (!$product_data) {
        $sql = "SELECT *, p.product_id, (SELECT AVG(rating) AS total FROM " . DB_PREFIX . "review r1 WHERE r1.product_id = p.product_id AND r1.status = '1' GROUP BY r1.product_id) AS rating FROM " . DB_PREFIX . "product p LEFT JOIN " . DB_PREFIX . "product_description pd ON (p.product_id = pd.product_id) LEFT JOIN " . DB_PREFIX . "product_to_store p2s ON (p.product_id = p2s.product_id) WHERE pd.language_id = '" . (int)$this->config->get('config_language_id') . "' AND p.status = '1' AND p.date_available <= NOW() AND p2s.store_id = '" . (int)$this->config->get('config_store_id') . "'"; 

        $sql .= " GROUP BY p.product_id";

        $sort_data = array(             'pd.name',
            'p.model',
            'p.quantity',
            'p.price',
            'rating',
            'p.sort_order',
            'p.date_added'
        );  

        $sql .= " ORDER BY Rand()";

        if (isset($data['order']) && ($data['order'] == 'DESC')) {
            $sql .= " DESC";
        } else {
            $sql .= " ASC";
        }

        if (isset($data['start']) || isset($data['limit'])) {
            if ($data['start'] < 0) {
                $data['start'] = 0;
            }               

            if ($data['limit'] < 1) {
                $data['limit'] = 20;
            }   

            $sql .= " LIMIT " . (int)$data['start'] . "," . (int)$data['limit'];
        }

        $product_data = array();    
        $query = $this->db->query($sql);

        foreach ($query->rows as $result) {
            $product_data[$result['product_id']] = $this->getProduct($result['product_id']);
        }

        $this->cache->set('product.' . $cache . '.' . $customer_group_id, $product_data);
    //}

    return $product_data;
}