Add sale price programmatically to product variations

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What you can try to do is to update expiration date meta_value to an outdated timestamp, this way: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This way you will force the system to rebuild this outdated cached transient.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

For April 2021, this is the code:

        $variation = wc_get_product_object( 'variation', $variation_id );
        $variation->set_props(
                array(
                    'regular_price' => $price,
                    'sale_price' => $sale_price,
                     )
            );
        $variation->save();

Source: function save_variations( $post_id, $post )

Answer 3

If you take a look at the Rest Api Controllers of the latest version of Woocommerce you can see that it is as easy as:

function set_price_to_variation($var_id, $price, $sale) {
    if ( !empty($var_id) ) {
        $variation = wc_get_product($var_id);
        $variation->set_regular_price($price);
        $variation->set_sale_price($sale);
        $variation->save();
    }
    return $variation;
}

Ref: \includes\rest-api\Controllers\Version3\class-wc-rest-product-variations-controller.php

Answer 4

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);