JCacheStorageDb for storing cache files in database from http://forum.joomla.org/viewtopic.php?p=1380543

gistfile1.php

<?php
// Check to ensure this file is within the rest of the framework
defined('JPATH_BASE') or die();

/**
 * DB cache storage handler
 *
 * @author		Geraint Edwards (http://www.gwesystems.com)
 * @package		Joomla.Framework
 * @subpackage	Cache
 * @since		1.5
 */
class JCacheStorageDb extends JCacheStorage
{
	var $cleanedExpired = false;

	/**
	* Constructor
	*
	* @access protected
	* @param array $options optional parameters
	*/
	function __construct( $options = array() )
	{
		parent::__construct($options);

		if (!$this->cleanedExpired) $this->gc();
	}

	/**
	 * One time only DB setup function
	 *
	 */
	function setupDB() {
		$db =& JFactory::getDBO();
		$sql = "CREATE TABLE IF NOT EXISTS `#__dbcache` ("
		. "\n `id` varchar ( 32 )  NOT NULL default '',"
		. "\n `groupname` varchar ( 32 ) NOT NULL default '',"
		. "\n `expire` datetime NOT NULL default '0000-00-00 00:00:00',"
		. "\n `value` TEXT NOT NULL default '',"
		. "\n PRIMARY KEY ( `id`,`groupname` ),"
		. "\n KEY ( `expire`,`groupname` )"
		. "\n ) CHARACTER SET utf8 COLLATE utf8_general_ci";
		$db->setQuery( $sql );
		if (!$db->query()){
			echo $db->getErrorMsg()."<br/>";
			echo $db->_sql;
		}
	}

	/**
	 * Get cached data from a db by id and group
	 *
	 * @access	public
	 * @param	string	$id			The cache data id
	 * @param	string	$group		The cache data group
	 * @param	boolean	$checkTime	True to verify cache time expiration threshold
	 * @return	mixed	Boolean false on failure or a cached data string
	 * @since	1.5
	 */
	function get($id, $group, $checkTime)
	{

		$data = false;

		$data = base64_encode($data);
		$db =& JFactory::getDBO();
		$sql = "SELECT  value FROM `#__dbcache` WHERE id=".$db->quote($id)." AND groupname=".$db->quote($group)." AND expire>FROM_UNIXTIME(".$db->quote($this->_now).")";
		$db->setQuery($sql);

		// Must set false to ensure that Joomfish doesn't get involved
		$data = $db->loadResult(false);
		if (is_null($data)){
			$data = false;
		}
		else {
			$data = base64_decode($data);
		}

		return $data;
	}

	/**
	 * Store the data to a file by id and group
	 *
	 * @access	public
	 * @param	string	$id		The cache data id
	 * @param	string	$group	The cache data group
	 * @param	string	$data	The data to store in cache
	 * @return	boolean	True on success, false otherwise
	 * @since	1.5
	 */
	function store($id, $group, $data)
	{
		$data = base64_encode($data);
		$db =& JFactory::getDBO();
		$sql = "REPLACE INTO `#__dbcache` (id, groupname,expire,value) VALUES (".$db->quote($id).",".$db->quote($group).",FROM_UNIXTIME(".$db->quote($this->_now + $this->_lifetime)."),".$db->quote($data).")";
		$db->setQuery($sql);
		return $db->query();
	}

	/**
	 * Remove a cached data file by id and group
	 *
	 * @access	public
	 * @param	string	$id		The cache data id
	 * @param	string	$group	The cache data group
	 * @return	boolean	True on success, false otherwise
	 * @since	1.5
	 */
	function remove($id, $group)
	{
		$db =& JFactory::getDBO();
		$sql = "DELETE FROM `#__dbcache` WHERE id=".$db->quote($id)." AND groupname=".$db->quote($group);
		$db->setQuery($sql);
		return $db->query();
	}

	/**
	 * Clean cache for a group given a mode.
	 *
	 * group mode		: cleans all cache in the group
	 * notgroup mode	: cleans all cache not in the group
	 *
	 * @access	public
	 * @param	string	$group	The cache data group
	 * @param	string	$mode	The mode for cleaning cache [group|notgroup]
	 * @return	boolean	True on success, false otherwise
	 * @since	1.5
	 */
	function clean($group, $mode)
	{
		switch (trim($mode))
		{
			case 'group':
				$db =& JFactory::getDBO();
				$sql = "DELETE FROM `#__dbcache` ";
				$db->setQuery($sql);
				return $db->query();
				break;
			default:
				$db =& JFactory::getDBO();
				$sql = "DELETE FROM `#__dbcache` WHERE groupname=".$db->quote($group);
				$db->setQuery($sql);
				return $db->query();
				break;
		}
		return $return;
	}

	/**
	 * Garbage collect expired cache data
	 *
	 * @access public
	 * @return boolean  True on success, false otherwise.
	 */
	function gc()
	{
		$db =& JFactory::getDBO();
		$sql = "DELETE FROM `#__dbcache` WHERE expire< FROM_UNIXTIME(".$db->quote($this->_now).")";
		$db->setQuery($sql);
		$result = $db->query();
		// if we can't delete then the database table probably doesn't exist so create it 
		if (!$result && $db->getErrorNum()==1146){
			$this->setupDB();
		}
	}

	/**
	 * Test to see if the cache storage is available.
	 *
	 * @static
	 * @access public
	 * @return boolean  True on success, false otherwise.
	 */
	function test()
	{
		return true;
	}


}