Add woocommerce variation GTIN to structured data - woocommerce

Question

If a webshop has variable products, in some cases the variations have unique GTINs. In our case, it is EAN.
How to add these different GTINS to the structured data? I made a function to insert multiple "offer" in "offers", but the GTIN is not recognized here.
This is the function:
//add structured data to the markup
function set_structured_data( $markup, $product ) {
if ($product->is_type('simple')){
$markup['brand'] = array('#type' => 'Brand', 'name' => get_post_meta( $product->get_id(), '_brand', true ) );
$markup['gtin8'] = get_post_meta( $product->get_id(), '_EAN', true );
}
if ($product->is_type('variable')){
$available_variations = $product->get_available_variations();
foreach ($available_variations as $variation) {
$variation_id = $variation['variation_id'];
$variproduct = wc_get_product($variation_id);
$i++;
$stock = $product->get_stock_status();
$offers[] = array(
'type' => 'Offer',
'price' => $variproduct->get_price(),
'priceValidUntil' => $priceuntil,
'priceSpecification' => array(
'price' => $variproduct->get_price(),
'priceCurrency' => get_woocommerce_currency(),
'valueAddedTaxIncluded' => 'http://schema.org/True'
),
'priceCurrency' => get_woocommerce_currency(),
'availability' => 'http://schema.org/'.$stock.'',
'url' => get_the_permalink(),
'seller' => array (
'type' => 'Organization',
'name' => 'HeatPerformance®',
'url' => get_the_permalink(),
));
}
$markup['offers'] = $offers;
$markup['brand'] = array('#type' => 'Brand', 'name' => get_post_meta( $product->get_id(), '_brand', true ) );
}
return $markup;
}
add_filter( 'woocommerce_structured_data_product', 'set_structured_data', 99, 2 );
Any ideas?

Answer 1

Ok after a couple of days puzzling i found the path to a solution here:
https://support.google.com/merchants/answer/6386198?hl=en
Result is that i corrected the standardized method from woocommerce and made each variation a unique product.
So first remove the markup in case of a variable product like this:
function set_structured_data( $markup, $product ) {
if ($product->is_type('variable')) {
$markup = array();
}
return $markup;
}
add_filter( 'woocommerce_structured_data_product', 'set_structured_data', 99, 2 );
And then build up the ld+json script again, but then the desired way:
function set_structured_data_variable() {
global $product;
if (isset($product)){
if ($product->is_type('variable') && !empty($product)){
$available_variations = $product->get_available_variations();
$date = date("Y-m-d",strtotime(" + 3months"));
$commenttext = '';
$commentauthor = '';
$commentdate = '';
$comments = get_comments(array( 'post_id' => $product->get_id(), 'number' => '1' ));
foreach($comments as $comment) {
$commenttext = $comment->comment_content;
$commentauthor = $comment->comment_author;
$commentdate = $comment->comment_date;
}
foreach ($available_variations as $variation) {
$variation_id = $variation['variation_id'];
$variproduct = wc_get_product($variation_id);
$i++;
$gtin = 0000000000001;
if (!empty(get_post_meta( $variation_id, '_EAN', true ))){
$gtin = get_post_meta( $variation_id, '_EAN', true );
}
$stock = $product->get_stock_status();
$arrays[$i] = array(
'#context' => 'https://schema.org/',
'#type' => 'Product',
'sku' => $variproduct->get_sku(),
'gtin13' => $gtin,
'image' => get_the_post_thumbnail_url($product->get_id()),
'name' => implode(" / ", $variproduct->get_variation_attributes()),
'description' => wp_strip_all_tags(get_the_excerpt($product->get_id())),
'brand' => array('#type' => 'Brand', 'name' => get_post_meta( $product->get_id(), '_brand', true ) ),
'review' => array(
'#type' => 'Review',
'reviewRating' => array (
'#type' => 'Rating',
'ratingValue' => $product->get_review_count(),
'bestRating' => '5',
'worstRating' => '1',
),
'author' => array(
'#type' => 'person',
'name' => $commentauthor,
'reviewBody' => $commenttext,
'datePublished' => $commentdate,
)),
'aggregateRating' => array (
'#type' => 'AggregateRating',
'ratingValue'=> $product->get_average_rating(),
'reviewCount' => $product->get_rating_count(),
),
'inProductGroupWithID' => $product->get_sku(),
'offers' => array(
'#type' => 'Offer',
'price' => $variproduct->get_price(),
'priceValidUntil' => $date,
'priceSpecification' => array(
'price' => $variproduct->get_price(),
'priceCurrency' => get_woocommerce_currency(),
'valueAddedTaxIncluded' => 'http://schema.org/True'
),
'priceCurrency' => get_woocommerce_currency(),
'availability' => 'http://schema.org/'.$stock.'',
'url' => get_the_permalink(),
'seller' => array (
'type' => 'Organization',
'name' => 'HeatPerformance®',
'url' => get_the_permalink(),
)));
}
echo '<script type="application/ld+json" class="buronoort">[';
$i = 0;
foreach ($arrays as $array){
$i++;
echo json_encode($array);
if ($i < array_key_last($arrays)){
echo ',';
}
}
echo ']</script>';
}
}
}
add_action('wp_head','set_structured_data_variable', 19);
Tested in the test tool for structured data and it is working.
A little concern is the product review however, i have to look into that what happens after multiple reviews.
Another concern is the EAN, i have set it standard to "0000000000001" as not all EANS are inputted yet. So this is a debatle solution, but if someone has a better idea, keep me posted.