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<?php
/**
* CDummyCache class file.
*
* @author Qiang Xue <[email protected]>
* @link http://www.yiiframework.com/
* @copyright Copyright © 2008-2011 Yii Software LLC
* @license http://www.yiiframework.com/license/
*/
/**
* CDummyCache is a placeholder cache component.
*
* CDummyCache does not cache anything. It is provided so that one can always configure
* a 'cache' application component and he does not need to check if Yii::app()->cache is null or not.
* By replacing CDummyCache with some other cache component, one can quickly switch from
* non-caching mode to caching mode.
*
* @author Qiang Xue <[email protected]>
* @version $Id: CDummyCache.php 2799 2011-01-01 19:31:13Z qiang.xue $
* @package system.caching
* @since 1.0
*/
class CDummyCache extends CApplicationComponent implements ICache, ArrayAccess
{
/**
* @var string a string prefixed to every cache key so that it is unique. Defaults to {@link CApplication::getId() application ID}.
*/
public $keyPrefix;
/**
* Initializes the application component.
* This method overrides the parent implementation by setting default cache key prefix.
*/
public function init()
{
parent::init();
if($this->keyPrefix===null)
$this->keyPrefix=Yii::app()->getId();
}
/**
* Retrieves a value from cache with a specified key.
* @param string $id a key identifying the cached value
* @return mixed the value stored in cache, false if the value is not in the cache, expired or the dependency has changed.
*/
public function get($id)
{
return false;
}
/**
* Retrieves multiple values from cache with the specified keys.
* Some caches (such as memcache, apc) allow retrieving multiple cached values at one time,
* which may improve the performance since it reduces the communication cost.
* In case a cache doesn't support this feature natively, it will be simulated by this method.
* @param array $ids list of keys identifying the cached values
* @return array list of cached values corresponding to the specified keys. The array
* is returned in terms of (key,value) pairs.
* If a value is not cached or expired, the corresponding array value will be false.
* @since 1.0.8
*/
public function mget($ids)
{
$results=array();
foreach($ids as $id)
$results[$id]=false;
return $results;
}
/**
* Stores a value identified by a key into cache.
* If the cache already contains such a key, the existing value and
* expiration time will be replaced with the new ones.
*
* @param string $id the key identifying the value to be cached
* @param mixed $value the value to be cached
* @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
* @param ICacheDependency $dependency dependency of the cached item. If the dependency changes, the item is labeled invalid.
* @return boolean true if the value is successfully stored into cache, false otherwise
*/
public function set($id,$value,$expire=0,$dependency=null)
{
return true;
}
/**
* Stores a value identified by a key into cache if the cache does not contain this key.
* Nothing will be done if the cache already contains the key.
* @param string $id the key identifying the value to be cached
* @param mixed $value the value to be cached
* @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
* @param ICacheDependency $dependency dependency of the cached item. If the dependency changes, the item is labeled invalid.
* @return boolean true if the value is successfully stored into cache, false otherwise
*/
public function add($id,$value,$expire=0,$dependency=null)
{
return true;
}
/**
* Deletes a value with the specified key from cache
* @param string $id the key of the value to be deleted
* @return boolean if no error happens during deletion
*/
public function delete($id)
{
return true;
}
/**
* Deletes all values from cache.
* Be careful of performing this operation if the cache is shared by multiple applications.
* @return boolean whether the flush operation was successful.
* @throws CException if this method is not overridden by child classes
*/
public function flush()
{
return true;
}
/**
* Returns whether there is a cache entry with a specified key.
* This method is required by the interface ArrayAccess.
* @param string $id a key identifying the cached value
* @return boolean
*/
public function offsetExists($id)
{
return false;
}
/**
* Retrieves the value from cache with a specified key.
* This method is required by the interface ArrayAccess.
* @param string $id a key identifying the cached value
* @return mixed the value stored in cache, false if the value is not in the cache or expired.
*/
public function offsetGet($id)
{
return false;
}
/**
* Stores the value identified by a key into cache.
* If the cache already contains such a key, the existing value will be
* replaced with the new ones. To add expiration and dependencies, use the set() method.
* This method is required by the interface ArrayAccess.
* @param string $id the key identifying the value to be cached
* @param mixed $value the value to be cached
*/
public function offsetSet($id, $value)
{
}
/**
* Deletes the value with the specified key from cache
* This method is required by the interface ArrayAccess.
* @param string $id the key of the value to be deleted
* @return boolean if no error happens during deletion
*/
public function offsetUnset($id)
{
}
}