protected function getFieldsCompare(array $products)
    {
        $labels = array();

        foreach ($products as $product) {
            if (!empty($product['field_value_labels'])) {
                foreach ($product['field_value_labels'] as $type => $fields) {
                    foreach (array_keys($fields) as $field_id) {
                        $labels[$type][$field_id] = $product['fields'][$type][$field_id]['title'];
                    }
                }
            }
        }

        return $labels;
    }