Update all variations prices of a variable product in Woocommerce

First in your code ‘ or ’ should be replaced by '. Also if used $post-ID should be replaced by $post->ID

Depending on where and how you are using this code, you should try to include global $post; first to be able to use the WP_Post object $post.

Then you could try to use this customized version of your code instead:

global $post;$regular_price = 13;// Only for product post typeif( $post->post_type == 'product' )    $product = wc_get_product( $post->ID ); // An instance of the WC_Product object// Only for variable productsif( $product->is_type('variable') ){    foreach( $product->get_available_variations() as $variation_values ){        $variation_id = $variation_values['variation_id']; // variation id        // Updating active price and regular price        update_post_meta( $variation_id, '_regular_price', $regular_price );        update_post_meta( $variation_id, '_price', $regular_price );        wc_delete_product_transients( $variation_id ); // Clear/refresh the variation cache    }    // Clear/refresh the variable product cache    wc_delete_product_transients( $post->ID );}

This code is tested on WooCommerce version 3+ and works