Magento – How to get the website Id’s a product is associated with

I had to set the StoreId, not the websiteId. Just needed to choose a store belonging to the desired website:

$product = Mage::getModel('catalog/product') -> loadByAttribute('sku', $sku);
$product->setStoreId(1) -> setPrice($price1) ->save() ;
$product->setStoreId(9) -> setPrice($price9) ->save();

Actions in layout xml configs are just a block method call. So if you see construction like

<block type     = "checkout/cart_sidebar" 
       name     = "cart_sidebar" 
       as       = "cartExplorer" 
       template = "checkout/cart/sidebar.phtml" 
       before   = "-">
<action method="addItemRender">
    <type>configurable</type>
    <block>checkout/cart_item_renderer_configurable</block>
    <template>checkout/cart/sidebar/default.phtml</template>
</action>

That is equivalent to

$this->getLayout()
     ->createBlock('checkout/cart_sidebar', 'cart_sidebar')
     ->setTemplate('checkout/cart/sidebar.phtml');
     ->addItemRender(
         'configurable', 
         'checkout/cart_item_renderer_configurable',
         'checkout/cart/sidebar/default.phtml'
     )

Or if block cart_sidebar was already created in layout xml

$this->getLayout()
     ->getBlock('cart_sidebar')
     ->addItemRender(
         'configurable', 
         'checkout/cart_item_renderer_configurable',
         'checkout/cart/sidebar/default.phtml'
     )