WooCommerce no attributes added and variations disappearing - php

Question

When I execute the code below, there will be added a product to WooCommerce Products with variations of the attributes 'pa_size' and 'pa_color' after I pushed a button.
When I preview the product, everything works fine.
However, when I'm going to edit and save that product, there are no attributes existing. On top of that, the variations disappear when I'm saving the product again.
I've searched the internet for at least three days, so if someone knows a proper solution I would be grateful.
Code:
class Product {
function __construct () {
// In a class constructor
$this->size_tax = wc_attribute_taxonomy_name( 'Size' );
$this->color_tax = wc_attribute_taxonomy_name( 'Color' );
}
function addProduct() {
// Insert the main product first
// It will be used as a parent for other variations (think of it as a container)
$product_id = wp_insert_post( array(
'post_title' => "Product Example",
'post_content' => "Product post content goes here...",
'post_status' => "publish",
'post_excerpt' => "This is the description",
'post_name' => "test_prod_vars2", //name/slug
'post_type' => "product"
) );
// Insert the attributes (I will be using size and color for variations)
$attributes = array(
$this->size_tax => array(
'name' => $this->size_tax,
'value' =>'',
'is_visible' => '1',
'is_variation' => '1',
'is_taxonomy' => '1'
),
$this->color_tax => array(
'name' => $this->color_tax,
'value' => '',
'is_visible' => '1',
'is_variation' => '1',
'is_taxonomy' => '1'
)
);
update_post_meta( $product_id, '_product_attributes', $attributes );
// Assign sizes and colors to the main product
// Set product type as variable
wp_set_object_terms( $product_id, 'variable', 'product_type', false );
// Start creating variations
$sizes = array('small', 'medium', 'large');
$prices = array('5', '10', '15');
$colors = array('red', 'white', 'blue');
for($i=0; $i<count($sizes); $i++) {
for($j=0; $j<count($colors); $j++) {
$parent_id = $product_id;
$variation = array(
'post_title' => 'Product #' . $parent_id . ' Variation',
'post_content' => '',
'post_status' => 'publish',
'post_parent' => $parent_id,
'post_type' => 'product_variation'
);
// The variation id
$variation_id = wp_insert_post( $variation );
update_post_meta( $variation_id, '_price', $prices[$i] );
// Assign the size and color of this variation
update_post_meta( $variation_id, 'attribute_' . $this->size_tax, $sizes[$i] );
update_post_meta( $variation_id, 'attribute_' . $this->color_tax, $colors[$j] );
// Update parent if variable so price sorting works and stays in sync with the cheapest child
WC_Product_Variable::sync( $parent_id );
}
}
}
}
if(isset($_POST['button'])) {
$product = new Product;
$product->addProduct();
}

Answer 1

If your attribute
'is_taxonomy' => '1'
then you have to insert taxonomy slug instead of text based value.
Try 'is_taxonomy' => '0' as a fast check.