对于店面，我使用此函数获取格式化价格：

<?php echo price_formatted(calculate_product_price($product->price, $product->discount_rate), $product->currency, false); ?>
<?php else:
if (!empty($product->discount_rate)): ?>
<?php echo price_formatted($product->price, $product->currency, true); ?>

使用此函数生成提要XML：

public function generate_google_post()
    {

    $xml   = '<channel>';
    $query = $this->sitemap_model->get_all_products();

    foreach ($query as $row) {
        $xml .= '<item>
            <g:id>'.$row['id'].'</g:id>
            <title>'.$row['title'].'</title>
            <link>https://mywebtest.com/'.$row['slug'].'</link>
            <g:price>'.$row['price'].' PLN</g:price>
            <description>'.$row['description'].'</description>
            <g:product_type>'.$row['category_id'].'</g:product_type>
            <g:google_product_category>'.$row['category_id'].'</g:google_product_category>
            <g:image_link>htts://mywebtest.com/upload/images'.$row['image_default'].'</g:image_link>
            <g:condition>new</g:condition>
            <g:availability>in stock</g:availability>
            <g:brand>'.$row['brand'].'</g:brand>
            <g:mpn>'.$row['sku'].'</g:mpn>
            <g:gtin>'.$row['ean'].'</g:gtin>
        </item>';
    }

    $xml .= '</channel>';

    header('Content-type: text/xml');
    header('Content-Disposition: attachment; filename="file.xml"');

    echo $xml;
    }

问题是目前我得到的输出价格没有格式化。
1.如何实现上述功能，将价格格式化后生成输出？