woocommerce_product_upsell_ids │ filter-hook │ WC 1.0

Usage

add_filter( 'woocommerce_product_upsell_ids', 'wp_kama_woocommerce_product_upsell_ids_filter', 10, 2 );

/**
 * Function for `woocommerce_product_upsell_ids` filter-hook.
 * 
 * @param  $upsell_ids 
 * @param  $that       
 *
 * @return 
 */
function wp_kama_woocommerce_product_upsell_ids_filter( $upsell_ids, $that ){

	// filter...
	return $upsell_ids;
}

$upsell_ids

-

$that

-

Where the hook is called

return apply_filters( 'woocommerce_product_upsell_ids', $this->get_upsell_ids(), $this );

Where the hook is used in WooCommerce