Add sale price programmatically to product variati

Question

I need to update the sale price programmatically, on variable product and all his variations.

What kind of meta field do I need to add?

I'm trying to update main product such as:

update_post_meta($post_id, '_regular_price', '100');
update_post_meta($post_id, '_price', '50');
update_post_meta($post_id, '_sale_price', '50');

and then I update every single variations

update_post_meta($variation_id, '_regular_price', '100');
update_post_meta($variation_id, '_price', '50');
update_post_meta($variation_id, '_sale_price', '50');
update_post_meta($variation_id, 'attribute_pa_taglia', $term_slug);
update_post_meta($variation_id, '_stock', $stock);
update_post_meta($variation_id, '_stock_status', 'instock');
update_post_meta($variation_id, '_manage_stock', 'yes');

Back end: product detail, everything ok

However backend (product list) and frontend get me old price

Answer 1

Update: Prices are also cached in transient wp_options table.

Let say your product ID is 222, you will have that transients meta_keys in wp_options table (for this product ID):

'_transient_timeout_wc_product_children_22'
'_transient_wc_product_children_22'
'_transient_timeout_wc_var_prices_222' // <=== <=== HERE
'_transient_wc_var_prices_222'    // <=== <=== <=== HERE

What you can try to do is to update expiration date meta_value to an outdated timestamp, this way:

// Set here your product ID
$main_product_id = 222
$transcient_product_meta_key = '_transient_wc_var_prices_'. $main_product_id;
update_option( $transcient_product_meta_key, strtotime("-12 hours") );
wp_cache_delete ( 'alloptions', 'options' ); // Refresh caches

This way you will force the system to rebuild this outdated cached transient.

---

Additionally you should try to add/update in your parent product ID (the main product where variation are set) these:

// Set here your Main product ID (for example the last variation ID of your product)
$post_id = 22;

// Set here your variation ID (for example the last variation ID of your product)
$variation_id = 24;

// Here your Regular price
$reg_price = 100;
// Here your Sale price
$sale_price = 50;

update_post_meta($post_id, '_min_variation_price', $sale_price);
update_post_meta($post_id, '_max_variation_price', $sale_price);
update_post_meta($post_id, '_min_variation_regular_price', $reg_price);
update_post_meta($post_id, '_max_variation_regular_price', $reg_price);
update_post_meta($post_id, '_min_variation_sale_price', $sale_price);
update_post_meta($post_id, '_max_variation_sale_price', $sale_price); 

update_post_meta($post_id, '_min_price_variation_id', $variation_id);
update_post_meta($post_id, '_max_price_variation_id', $variation_id);
update_post_meta($post_id, '_min_regular_price_variation_id', $variation_id);
update_post_meta($post_id, '_max_regular_price_variation_id', $variation_id);
update_post_meta($post_id, '_min_sale_price_variation_id', $variation_id);
update_post_meta($post_id, '_max_sale_price_variation_id', $variation_id);

// Optionally
wc_delete_product_transients($variation_id);

Answer 2

Furthermore, I've find other solution that work same:

$product_variable = new WC_Product_Variable($post_id);
$product_variable->sync($post_id);
wc_delete_product_transients($post_id);