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CCache

Package system.caching
Inheritance abstract class CCache » CApplicationComponent » CComponent
Implements IApplicationComponent, ICache, ArrayAccess
Subclasses CApcCache, CDbCache, CEAcceleratorCache, CFileCache, CMemCache, CRedisCache, CWinCache, CXCache, CZendDataCache
Since 1.0
Source Code framework/caching/CCache.php
CCache is the base class for cache classes with different cache storage implementation.

A data item can be stored in cache by calling set and be retrieved back later by get. In both operations, a key identifying the data item is required. An expiration time and/or a dependency can also be specified when calling set. If the data item expires or the dependency changes, calling get will not return back the data item.

Note, by definition, cache does not ensure the existence of a value even if it does not expire. Cache is not meant to be a persistent storage.

CCache implements the interface ICache with the following methods:
  • get : retrieve the value with a key (if any) from cache
  • set : store the value with a key into cache
  • add : store the value only if cache does not have this key
  • delete : delete the value with the specified key from cache
  • flush : delete all values from cache


Child classes must implement the following methods:

CCache also implements ArrayAccess so that it can be used like an array.

Public Properties

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PropertyTypeDescriptionDefined By
behaviors array the behaviors that should be attached to this component. CApplicationComponent
hashKey boolean whether to md5-hash the cache key for normalization purposes. CCache
isInitialized boolean Checks if this application component has been initialized. CApplicationComponent
keyPrefix string a string prefixed to every cache key so that it is unique. CCache
serializer array|boolean the functions used to serialize and unserialize cached data. CCache

Public Methods

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MethodDescriptionDefined By
__call() Calls the named method which is not a class method. CComponent
__get() Returns a property value, an event handler list or a behavior based on its name. CComponent
__isset() Checks if a property value is null. CComponent
__set() Sets value of a component property. CComponent
__unset() Sets a component property to be null. CComponent
add() Stores a value identified by a key into cache if the cache does not contain this key. CCache
asa() Returns the named behavior object. CComponent
attachBehavior() Attaches a behavior to this component. CComponent
attachBehaviors() Attaches a list of behaviors to the component. CComponent
attachEventHandler() Attaches an event handler to an event. CComponent
canGetProperty() Determines whether a property can be read. CComponent
canSetProperty() Determines whether a property can be set. CComponent
delete() Deletes a value with the specified key from cache CCache
detachBehavior() Detaches a behavior from the component. CComponent
detachBehaviors() Detaches all behaviors from the component. CComponent
detachEventHandler() Detaches an existing event handler. CComponent
disableBehavior() Disables an attached behavior. CComponent
disableBehaviors() Disables all behaviors attached to this component. CComponent
enableBehavior() Enables an attached behavior. CComponent
enableBehaviors() Enables all behaviors attached to this component. CComponent
evaluateExpression() Evaluates a PHP expression or callback under the context of this component. CComponent
flush() Deletes all values from cache. CCache
get() Retrieves a value from cache with a specified key. CCache
getEventHandlers() Returns the list of attached event handlers for an event. CComponent
getIsInitialized() Checks if this application component has been initialized. CApplicationComponent
hasEvent() Determines whether an event is defined. CComponent
hasEventHandler() Checks whether the named event has attached handlers. CComponent
hasProperty() Determines whether a property is defined. CComponent
init() Initializes the application component. CCache
mget() Retrieves multiple values from cache with the specified keys. CCache
offsetExists() Returns whether there is a cache entry with a specified key. CCache
offsetGet() Retrieves the value from cache with a specified key. CCache
offsetSet() Stores the value identified by a key into cache. CCache
offsetUnset() Deletes the value with the specified key from cache CCache
raiseEvent() Raises an event. CComponent
set() Stores a value identified by a key into cache. CCache

Protected Methods

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MethodDescriptionDefined By
addValue() Stores a value identified by a key into cache if the cache does not contain this key. CCache
deleteValue() Deletes a value with the specified key from cache CCache
flushValues() Deletes all values from cache. CCache
generateUniqueKey() CCache
getValue() Retrieves a value from cache with a specified key. CCache
getValues() Retrieves multiple values from cache with the specified keys. CCache
setValue() Stores a value identified by a key in cache. CCache

Property Details

hashKey property (available since v1.1.11)
public boolean $hashKey;

whether to md5-hash the cache key for normalization purposes. Defaults to true. Setting this property to false makes sure the cache key will not be tampered when calling the relevant methods get(), set(), add() and delete(). This is useful if a Yii application as well as an external application need to access the same cache pool (also see description of keyPrefix regarding this use case). However, without normalization you should make sure the affected cache backend does support the structure (charset, length, etc.) of all the provided cache keys, otherwise there might be unexpected behavior.

keyPrefix property
public string $keyPrefix;

a string prefixed to every cache key so that it is unique. Defaults to null which means to use the application ID. If different applications need to access the same pool of cached data, the same prefix should be set for each of the applications explicitly.

serializer property
public array|boolean $serializer;

the functions used to serialize and unserialize cached data. Defaults to null, meaning using the default PHP `serialize()` and `unserialize()` functions. If you want to use some more efficient serializer (e.g. igbinary), you may configure this property with a two-element array. The first element specifies the serialization function, and the second the deserialization function. If this property is set false, data will be directly sent to and retrieved from the underlying cache component without any serialization or deserialization. You should not turn off serialization if you are using cache dependency, because it relies on data serialization.

Method Details

add() method
public boolean add(string $id, mixed $value, integer $expire=0, ICacheDependency $dependency=NULL)
$id string the key identifying the value to be cached
$value mixed the value to be cached
$expire integer the number of seconds in which the cached value will expire. 0 means never expire.
$dependency ICacheDependency dependency of the cached item. If the dependency changes, the item is labeled invalid.
{return} boolean true if the value is successfully stored into cache, false otherwise
Source Code: framework/caching/CCache.php#197 (show)
public function add($id,$value,$expire=0,$dependency=null)
{
    Yii::trace('Adding "'.$id.'" to cache','system.caching.'.get_class($this));

    if ($dependency !== null && $this->serializer !== false)
        $dependency->evaluateDependency();

    if ($this->serializer === null)
        $value = serialize(array($value,$dependency));
    elseif ($this->serializer !== false)
        $value = call_user_func($this->serializer[0], array($value,$dependency));

    return $this->addValue($this->generateUniqueKey($id), $value, $expire);
}

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.

addValue() method
protected boolean addValue(string $key, string $value, integer $expire)
$key string the key identifying the value to be cached
$value string the value to be cached
$expire integer the number of seconds in which the cached value will expire. 0 means never expire.
{return} boolean true if the value is successfully stored into cache, false otherwise
Source Code: framework/caching/CCache.php#299 (show)
protected function addValue($key,$value,$expire)
{
    throw new CException(Yii::t('yii','{className} does not support add() functionality.',
        array('{className}'=>get_class($this))));
}

Stores a value identified by a key into cache if the cache does not contain this key. This method should be implemented by child classes to store the data in specific cache storage. The uniqueness and dependency are handled in add() already. So only the implementation of data storage is needed.

delete() method
public boolean delete(string $id)
$id string the key of the value to be deleted
{return} boolean if no error happens during deletion
Source Code: framework/caching/CCache.php#217 (show)
public function delete($id)
{
    Yii::trace('Deleting "'.$id.'" from cache','system.caching.'.get_class($this));
    return $this->deleteValue($this->generateUniqueKey($id));
}

Deletes a value with the specified key from cache

deleteValue() method
protected boolean deleteValue(string $key)
$key string the key of the value to be deleted
{return} boolean if no error happens during deletion
Source Code: framework/caching/CCache.php#312 (show)
protected function deleteValue($key)
{
    throw new CException(Yii::t('yii','{className} does not support delete() functionality.',
        array('{className}'=>get_class($this))));
}

Deletes a value with the specified key from cache This method should be implemented by child classes to delete the data from actual cache storage.

flush() method
public boolean flush()
{return} boolean whether the flush operation was successful.
Source Code: framework/caching/CCache.php#228 (show)
public function flush()
{
    Yii::trace('Flushing cache','system.caching.'.get_class($this));
    return $this->flushValues();
}

Deletes all values from cache. Be careful of performing this operation if the cache is shared by multiple applications.

flushValues() method (available since v1.1.5)
protected boolean flushValues()
{return} boolean whether the flush operation was successful.
Source Code: framework/caching/CCache.php#325 (show)
protected function flushValues()
{
    throw new CException(Yii::t('yii','{className} does not support flushValues() functionality.',
        array('{className}'=>get_class($this))));
}

Deletes all values from cache. Child classes may implement this method to realize the flush operation.

generateUniqueKey() method
protected string generateUniqueKey(string $key)
$key string a key identifying a value to be cached
{return} string a key generated from the provided key which ensures the uniqueness across applications
Source Code: framework/caching/CCache.php#92 (show)
protected function generateUniqueKey($key)
{
    return $this->hashKey ? md5($this->keyPrefix.$key) : $this->keyPrefix.$key;
}

get() method
public mixed get(string $id)
$id string a key identifying the cached value
{return} mixed the value stored in cache, false if the value is not in the cache, expired or the dependency has changed.
Source Code: framework/caching/CCache.php#102 (show)
public function get($id)
{
    $value = $this->getValue($this->generateUniqueKey($id));
    if($value===false || $this->serializer===false)
        return $value;
    if($this->serializer===null)
        $value=unserialize($value);
    else
        $value=call_user_func($this->serializer[1], $value);
    if(is_array($value) && (!$value[1] instanceof ICacheDependency || !$value[1]->getHasChanged()))
    {
        Yii::trace('Serving "'.$id.'" from cache','system.caching.'.get_class($this));
        return $value[0];
    }
    else
        return false;
}

Retrieves a value from cache with a specified key.

getValue() method
protected string|boolean getValue(string $key)
$key string a unique key identifying the cached value
{return} string|boolean the value stored in cache, false if the value is not in the cache or expired.
Source Code: framework/caching/CCache.php#244 (show)
protected function getValue($key)
{
    throw new CException(Yii::t('yii','{className} does not support get() functionality.',
        array('{className}'=>get_class($this))));
}

Retrieves a value from cache with a specified key. This method should be implemented by child classes to retrieve the data from specific cache storage. The uniqueness and dependency are handled in get() already. So only the implementation of data retrieval is needed.

getValues() method
protected array getValues(array $keys)
$keys array a list of keys identifying the cached values
{return} array a list of cached values indexed by the keys
Source Code: framework/caching/CCache.php#259 (show)
protected function getValues($keys)
{
    $results=array();
    foreach($keys as $key)
        $results[$key]=$this->getValue($key);
    return $results;
}

Retrieves multiple values from cache with the specified keys. The default implementation simply calls getValue multiple times to retrieve the cached values one by one. If the underlying cache storage supports multiget, this method should be overridden to exploit that feature.

init() method
public void init()
Source Code: framework/caching/CCache.php#81 (show)
public function init()
{
    parent::init();
    if($this->keyPrefix===null)
        $this->keyPrefix=Yii::app()->getId();
}

Initializes the application component. This method overrides the parent implementation by setting default cache key prefix.

mget() method
public array mget(array $ids)
$ids array list of keys identifying the cached values
{return} array list of cached values corresponding to the specified keys. The array is returned in terms of (key,value) pairs. If a value is not cached or expired, the corresponding array value will be false.
Source Code: framework/caching/CCache.php#130 (show)
public function mget($ids)
{
    $uids = array();
    foreach ($ids as $id)
        $uids[$id] = $this->generateUniqueKey($id);

    $values = $this->getValues($uids);
    $results = array();
    if($this->serializer === false)
    {
        foreach ($uids as $id => $uid)
            $results[$id] = isset($values[$uid]) ? $values[$uid] : false;
    }
    else
    {
        foreach($uids as $id => $uid)
        {
            $results[$id] = false;
            if(isset($values[$uid]))
            {
                $value = $this->serializer === null ? unserialize($values[$uid]) : call_user_func($this->serializer[1], $values[$uid]);
                if(is_array($value) && (!$value[1] instanceof ICacheDependency || !$value[1]->getHasChanged()))
                {
                    Yii::trace('Serving "'.$id.'" from cache','system.caching.'.get_class($this));
                    $results[$id] = $value[0];
                }
            }
        }
    }
    return $results;
}

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 does not support this feature natively, it will be simulated by this method.

offsetExists() method
public boolean offsetExists(string $id)
$id string a key identifying the cached value
{return} boolean
Source Code: framework/caching/CCache.php#338 (show)
public function offsetExists($id)
{
    return $this->get($id)!==false;
}

Returns whether there is a cache entry with a specified key. This method is required by the interface ArrayAccess.

offsetGet() method
public mixed offsetGet(string $id)
$id string a key identifying the cached value
{return} mixed the value stored in cache, false if the value is not in the cache or expired.
Source Code: framework/caching/CCache.php#350 (show)
public function offsetGet($id)
{
    return $this->get($id);
}

Retrieves the value from cache with a specified key. This method is required by the interface ArrayAccess.

offsetSet() method
public void offsetSet(string $id, mixed $value)
$id string the key identifying the value to be cached
$value mixed the value to be cached
Source Code: framework/caching/CCache.php#364 (show)
public function offsetSet($id, $value)
{
    $this->set($id, $value);
}

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.

offsetUnset() method
public void offsetUnset(string $id)
$id string the key of the value to be deleted
Source Code: framework/caching/CCache.php#375 (show)
public function offsetUnset($id)
{
    $this->delete($id);
}

Deletes the value with the specified key from cache This method is required by the interface ArrayAccess.

set() method
public boolean set(string $id, mixed $value, integer $expire=0, ICacheDependency $dependency=NULL)
$id string the key identifying the value to be cached
$value mixed the value to be cached
$expire integer the number of seconds in which the cached value will expire. 0 means never expire.
$dependency ICacheDependency dependency of the cached item. If the dependency changes, the item is labeled invalid.
{return} boolean true if the value is successfully stored into cache, false otherwise
Source Code: framework/caching/CCache.php#173 (show)
public function set($id,$value,$expire=0,$dependency=null)
{
    Yii::trace('Saving "'.$id.'" to cache','system.caching.'.get_class($this));

    if ($dependency !== null && $this->serializer !== false)
        $dependency->evaluateDependency();

    if ($this->serializer === null)
        $value = serialize(array($value,$dependency));
    elseif ($this->serializer !== false)
        $value = call_user_func($this->serializer[0], array($value,$dependency));

    return $this->setValue($this->generateUniqueKey($id), $value, $expire);
}

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.

setValue() method
protected boolean setValue(string $key, string $value, integer $expire)
$key string the key identifying the value to be cached
$value string the value to be cached
$expire integer the number of seconds in which the cached value will expire. 0 means never expire.
{return} boolean true if the value is successfully stored into cache, false otherwise
Source Code: framework/caching/CCache.php#280 (show)
protected function setValue($key,$value,$expire)
{
    throw new CException(Yii::t('yii','{className} does not support set() functionality.',
        array('{className}'=>get_class($this))));
}

Stores a value identified by a key in cache. This method should be implemented by child classes to store the data in specific cache storage. The uniqueness and dependency are handled in set() already. So only the implementation of data storage is needed.