I am trying to grammatically assign second 'seller' to user when the Woocommerce transaction is completed. I know that:
wp_update_user( array( 'ID' => $user_id, 'role' => 'seller' ) );
will change the role but how about adding the new one to existing serialized array. What I need in wp_capabilities is a:2:{s:7:"partner";b:1;s:6:"seller";b:1;}
Thank you!