Cache a particular block or html in Magento

Hi, we can cache the block and also we can cache the particular HTML block code 1st time it will cache and from next time it will call from cache for eg:- in product view page your list a information in for each loop so each time it will kill your performance so 1st time cache and next time load it from cache we can cache in 2 ways 1. Cache a Block in block php add below code ex List.php

 public function __construct()
    {
        $this->addData(array(
            'cache_lifetime'    => 1800,
            'cache_tags'        => array(Mage_Catalog_Model_Product::CACHE_TAG),
            'cache_key'         => $this->getCacheKey()
        ));
    } 

    public function getCacheKey()
    {
        return $this->getRequest()->getRequestUri().$this->getCacheCurrencyCode();
    }

    //retreive current currency code
    public function getCacheCurrencyCode()
    {
        return Mage::app()->getStore()->getCurrentCurrencyCode();
    } 

2. cache a particular html block (only html code will cache it will not cache any objects ) you can do below logic even by creating new block file and can call it in product view page if you dont want to create new block for this small things you can cache the information

 <?php 
$cache = Mage::getSingleton('core/cache');
$cacheTag    = array(
Mage_Catalog_Model_Product::CACHE_TAG,
);
$currentCurrencyCode = Mage::app()->getStore()->getCurrentCurrencyCode();
$storeId = Mage::app()->getStore()->getId();
$plantationkey=str_replace(' ', '_', $plantation);
$cacheKey    = 'Origin_' .$plantationkey . $storeId .$currentCurrencyCode;
$orginhtml = $cache->load($cacheKey);

if(!empty($orginhtml)){
    echo $orginhtml;
}else{
    $theProductBlock = new Mage_Catalog_Block_Product;
    $Bestsellerproducts = Mage::getResourceModel('catalog/product_collection')
                    ->addAttributeToSelect('*')
                    ->addFieldToFilter(array(array('attribute'=>'bestseller','in'=>1)))
                    ->addAttributeToFilter('visibility', $this->visibility)
                    ->addAttributeToFilter('status', Mage_Catalog_Model_Product_Status::STATUS_ENABLED)
                    ->addCategoryFilter($category); ?>

    <?php if(count($Bestsellerproducts)):?>
    <?php 
    $orginhtml ='<ul>';
    foreach($Bestsellerproducts as $bestseller){ 
    $orginhtml .='<li>
        <h2>'.$bestseller->getName().'</h2>
        <a href="'.$bestseller->getProductUrl().'" class="product-img"><img src="'.$this->helper('catalog/image')->init($bestseller, 'small_image')->resize(229).'" width="229" height="229" alt="'.$this->stripTags($this->getImageLabel($bestseller, 'small_image'), null, true).'" title="'.$bestseller->getName().'" /></a>
        <h2 class="product-name"><a href="'.$bestseller->getProductUrl().'">'.$bestseller->getName().'</a>
        </li>';
    }
 endif; ?>    


<?php echo $orginhtml; ?>
<?php $cache->save($orginhtml, $cacheKey, $cacheTag, 3600); ?>
<?php }    ?> 

http://www.magentocommerce.com/boards/viewthread/700444/