////checkbox ellenorzes
add_filter( 'woocommerce_add_cart_item_data', 'bbloomer_store_gift', 10, 2 );
function bbloomer_store_gift( $cart_item, $product_id ) {
      if( isset( $_POST['is-gift'] ) && $_POST['is-gift'] == "igen" ) {
            add_action( 'woocommerce_add_to_cart', 'aaptc_add_product_to_cart', 10, 2 );
      }
return $cart_item;
}

////maga a funkcio
function aaptc_add_product_to_cart( $item_key, $product_id ) {
      global $woocommerce;
      $free_product_id = 8692;
      $found = false;
      $quantity = 1;

      remove_action( 'woocommerce_add_to_cart', 'aaptc_add_product_to_cart', 10, 2 );
      WC()->cart->add_to_cart( $free_product_id, $quantity );
}