If we are required to have a custom module and wanted to save some data in magento cache, we will use cache in our custom modules.

To save the data in cache lets see,

$data = array(1,2,3,4); 
$id = 'my_mod_id'; 
$tags = array('collection');
$lifetime = false; 
$priority = 8; 

Any data which we want to save to cache is stored in $data and the unique id for our cache data is stored in $id. Then we assigned the $liftime false because false means infinity, or you can specify number of seconds. The priority is set by the parameter $priority as 0 (number between 0-9, used by few backend cache models).

Some basic cache functions are :

Retrieving Data

Mage::app()->loadCache($id);

Deleting Cache

Mage::app()->removeCache($id);

Checking If Cache Is Enabled

Mage::app()->useCache('collection');

Cache tags

Magento has concept of the cache tags in which magento basicallly uses tags to group cache data together.

The different cache tags we have are “block_html”,”collections”,”config”,”config_api”,”config_api2″,”eav”,”layout”,”translate” ,”mage” etc.

System -> Cache Management contains the these configuration tags.

Whenever any template is called in magento the tohtml() function is called which will check if $this->_loadCache() is enabled in admin and cache data is present or not. If it is present it will display it. 

Flush Magento Cache: This operation calls the function Mage::app()->cleanCache(); function. This function clears all cache tags data.

Flush Cache Storage: This function simply clear up the cache based on caching system. e.g in file storage this will delete all data in “var/cache” folder and in memcache it will delete all data in memcache.