# Abstract Class yii\caching\Cache

Inheritance | yii\caching\Cache » yii\base\Component » yii\base\BaseObject
Implements | yii\base\Configurable, yii\caching\CacheInterface
Subclasses | yii\caching\ApcCache, yii\caching\ArrayCache, yii\caching\DbCache, yii\caching\DummyCache, yii\caching\FileCache, yii\caching\MemCache, yii\caching\WinCache, yii\caching\XCache, yii\caching\ZendDataCache, yii\mongodb\Cache, yii\redis\Cache
Available since version | 2.0
Source Code | https://github.com/yiisoft/yii2/blob/master/framework/caching/Cache.php

Cache is the base class for cache classes supporting different cache storage implementations.

A data item can be stored in the cache by calling set() and be retrieved back later (in the same or different request) 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 at the time of calling get(), the cache will return no data.

A typical usage pattern of cache is like the following:

    $key = 'demo';
    $data = $cache->get($key);
    if ($data === false) {
        // ...generate $data here...
        $cache->set($key, $data, $duration, $dependency);
    }

Because Cache implements the ArrayAccess interface, it can be used like an array. For example,

    $cache['foo'] = 'some data';
    echo $cache['foo'];

Derived classes should implement the following methods which do the actual cache storage operations:

- getValue(): retrieve the value with a key (if any) from cache
- setValue(): store the value with a key into cache
- addValue(): store the value only if the cache does not have this key before
- deleteValue(): delete the value with the specified key from cache
- flushValues(): delete all values from cache

For more details and usage information on Cache, see the guide article on caching.

## Public Properties

Hide inherited properties

Property | Type | Description | Defined By
--- | --- | --- | ---
$behaviors | yii\base\Behavior[] | List of behaviors attached to this component. This property is read-only. | yii\base\Component
$defaultDuration | integer | Default duration in seconds before a cache entry will expire. | yii\caching\Cache
$keyPrefix | string | A string prefixed to every cache key so that it is unique globally in the whole cache storage. | yii\caching\Cache
$serializer | null|array|false | The functions used to serialize and unserialize cached data. | yii\caching\Cache

## Public Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
__call() | Calls the named method which is not a class method. | yii\base\Component
__clone() | This method is called after the object is created by cloning an existing one. | yii\base\Component
__construct() | Constructor. | yii\base\BaseObject
__get() | Returns the value of a component property. | yii\base\Component
__isset() | Checks if a property is set, i.e. defined and not null. | yii\base\Component
__set() | Sets the value of a component property. | yii\base\Component
__unset() | Sets a component property to be null. | yii\base\Component
add() | Stores a value identified by a key into cache if the cache does not contain this key. | yii\caching\Cache
attachBehavior() | Attaches a behavior to this component. | yii\base\Component
attachBehaviors() | Attaches a list of behaviors to the component. | yii\base\Component
behaviors() | Returns a list of behaviors that this component should behave as. | yii\base\Component
buildKey() | Builds a normalized cache key from a given key. | yii\caching\Cache
canGetProperty() | Returns a value indicating whether a property can be read. | yii\base\Component
canSetProperty() | Returns a value indicating whether a property can be set. | yii\base\Component
className() | Returns the fully qualified name of this class. | yii\base\BaseObject
delete() | Deletes a value with the specified key from cache. | yii\caching\Cache
detachBehavior() | Detaches a behavior from the component. | yii\base\Component
detachBehaviors() | Detaches all behaviors from the component. | yii\base\Component
ensureBehaviors() | Makes sure that the behaviors declared in behaviors() are attached to this component. | yii\base\Component
exists() | Checks whether a specified key exists in the cache. | yii\caching\Cache
flush() | Deletes all values from cache. | yii\caching\Cache
get() | Retrieves a value from cache with a specified key. | yii\caching\Cache
getBehavior() | Returns the named behavior object. | yii\base\Component
getBehaviors() | Returns all behaviors attached to this component. | yii\base\Component
getOrSet() | Method combines both set() and get() methods to retrieve value identified by a $key, or to store the result of $callable execution if there is no cache available for the $key. | yii\caching\Cache
hasEventHandlers() | Returns a value indicating whether there is any handler attached to the named event. | yii\base\Component
hasMethod() | Returns a value indicating whether a method is defined. | yii\base\Component
hasProperty() | Returns a value indicating whether a property is defined for this component. | yii\base\Component
init() | Initializes the object. | yii\caching\Cache
madd() | Stores multiple items in cache. Each item contains a value identified by a key. | yii\caching\Cache
mget() | Retrieves multiple values from cache with the specified keys. | yii\caching\Cache
mset() | Stores multiple items in cache. Each item contains a value identified by a key. | yii\caching\Cache
multiAdd() | Stores multiple items in cache. Each item contains a value identified by a key. | yii\caching\Cache
multiGet() | Retrieves multiple values from cache with the specified keys. | yii\caching\Cache
multiSet() | Stores multiple items in cache. Each item contains a value identified by a key. | yii\caching\Cache
off() | Detaches an existing event handler from this component. | yii\base\Component
offsetExists() | Returns whether there is a cache entry with a specified key. | yii\caching\Cache
offsetGet() | Retrieves the value from cache with a specified key. | yii\caching\Cache
offsetSet() | Stores the value identified by a key into cache. | yii\caching\Cache
offsetUnset() | Deletes the value with the specified key from cache This method is required by the interface ArrayAccess. | yii\caching\Cache
on() | Attaches an event handler to an event. | yii\base\Component
set() | Stores a value identified by a key into cache. | yii\caching\Cache
trigger() | Triggers an event. | yii\base\Component

## Protected Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
addValue() | Stores a value identified by a key into cache if the cache does not contain this key. | yii\caching\Cache
addValues() | Adds multiple key-value pairs to cache. | yii\caching\Cache
deleteValue() | 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. | yii\caching\Cache
flushValues() | Deletes all values from cache. | yii\caching\Cache
getValue() | Retrieves a value from cache with a specified key. | yii\caching\Cache
getValues() | Retrieves multiple values from cache with the specified keys. | yii\caching\Cache
setValue() | Stores a value identified by a key in cache. | yii\caching\Cache
setValues() | Stores multiple key-value pairs in cache. | yii\caching\Cache

## Property Details

$defaultDuration public property (available since version 2.0.11)

Default duration in seconds before a cache entry will expire. Default value is 0, meaning infinity. This value is used by set() if the duration is not explicitly given.

public integer $defaultDuration = 0
$keyPrefix public property

A string prefixed to every cache key so that it is unique globally in the whole cache storage. It is recommended that you set a unique cache key prefix for each application if the same cache storage is being used by different applications.

To ensure interoperability, only alphanumeric characters should be used.

public string $keyPrefix = null
$serializer public property

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. Also, some implementations of the cache can not correctly save and retrieve data different from a string type.

public null|array|false $serializer = null

## Method Details

add() public method

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.

public boolean add ( $key, $value, $duration = 0, $dependency = null )
$key | mixed | A key identifying the value to be cached. This can be a simple string or a complex data structure consisting of factors representing the key.
$value | mixed | The value to be cached
$duration | integer | The number of seconds in which the cached value will expire. 0 means never expire.
$dependency | yii\caching\Dependency | Dependency of the cached item. If the dependency changes, the corresponding value in the cache will be invalidated when it is fetched via get(). This parameter is ignored if $serializer is false.
return | boolean | Whether the value is successfully stored into cache

addValue() protected abstract method

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.

protected abstract boolean addValue ( $key, $value, $duration )
$key | string | The key identifying the value to be cached
$value | mixed | The value to be cached. Most often it's a string. If you have disabled $serializer, it could be something else.
$duration | 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

addValues() protected method

Adds multiple key-value pairs to cache.

The default implementation calls addValue() multiple times add values one by one. If the underlying cache storage supports multi-add, this method should be overridden to exploit that feature.

protected array addValues ( $data, $duration )
$data | array | Array where key corresponds to cache key while value is the value stored.
$duration | integer | The number of seconds in which the cached values will expire. 0 means never expire.
return | array | Array of failed keys

buildKey() public method

Builds a normalized cache key from a given key.

If the given key is a string containing alphanumeric characters only and no more than 32 characters, then the key will be returned back prefixed with $keyPrefix. Otherwise, a normalized key is generated by serializing the given key, applying MD5 hashing, and prefixing with $keyPrefix.

public string buildKey ( $key )
$key | mixed | The key to be normalized
return | string | The generated cache key

delete() public method

Deletes a value with the specified key from cache.

public boolean delete ( $key )
$key | mixed | A key identifying the value to be deleted from cache. This can be a simple string or a complex data structure consisting of factors representing the key.
return | boolean | If no error happens during deletion

deleteValue() protected abstract method

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.

protected abstract boolean deleteValue ( $key )
$key | string | The key of the value to be deleted
return | boolean | If no error happens during deletion

exists() public method

Checks whether a specified key exists in the cache.

This can be faster than getting the value from the cache if the data is big. In case a cache does not support this feature natively, this method will try to simulate it but has no performance improvement over getting it. Note that this method does not check whether the dependency associated with the cached data, if there is any, has changed. So a call to get() may return false while exists returns true.

public boolean exists ( $key )
$key | mixed | A key identifying the cached value. This can be a simple string or a complex data structure consisting of factors representing the key.
return | boolean | True if a value exists in cache, false if the value is not in the cache or expired.

flush() public method

Deletes all values from cache.

Be careful of performing this operation if the cache is shared among multiple applications.

public boolean flush ( )
return | boolean | Whether the flush operation was successful.

flushValues() protected abstract method

Deletes all values from cache.

Child classes may implement this method to realize the flush operation.

protected abstract boolean flushValues ( )
return | boolean | Whether the flush operation was successful.

get() public method

Retrieves a value from cache with a specified key.

public mixed get ( $key )
$key | mixed | A key identifying the cached value. This can be a simple string or a complex data structure consisting of factors representing the key.
return | mixed | The value stored in cache, false if the value is not in the cache, expired, or the dependency associated with the cached data has changed.

getOrSet() public method (available since version 2.0.11)

Method combines both set() and get() methods to retrieve value identified by a $key, or to store the result of $callable execution if there is no cache available for the $key.

Usage example:

    public function getTopProducts($count = 10) {
        $cache = $this->cache; // Could be Yii::$app->cache
        return $cache->getOrSet(['top-n-products', 'n' => $count], function () use ($count) {
            return Products::find()->mostPopular()->limit($count)->all();
        }, 1000);
    }

public mixed getOrSet ( $key, $callable, $duration = null, $dependency = null )
$key | mixed | A key identifying the value to be cached. This can be a simple string or a complex data structure consisting of factors representing the key.

$callable

callable|Closure

The callable or closure that will be used to generate a value to be cached. If you use $callable that can return `false`, then keep in mind that getOrSet() may work inefficiently because the yii\caching\Cache::get() method uses `false` return value to indicate the data item is not found in the cache. Thus, caching of `false` value will lead to unnecessary internal calls.

$duration | integer | Default duration in seconds before the cache will expire. If not set, $defaultDuration value will be used.
$dependency | yii\caching\Dependency | Dependency of the cached item. If the dependency changes, the corresponding value in the cache will be invalidated when it is fetched via get(). This parameter is ignored if $serializer is `false`.
return | mixed | Result of $callable execution

getValue() protected abstract method

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.

protected abstract mixed|false getValue ( $key )
$key | string | A unique key identifying the cached value
return | mixed|false | The value stored in cache, false if the value is not in the cache or expired. Most often value is a string. If you have disabled $serializer, it could be something else.

getValues() protected method

Retrieves multiple values from cache with the specified keys.

The default implementation 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.

protected array getValues ( $keys )
$keys | array | A list of keys identifying the cached values
return | array | A list of cached values indexed by the keys

init() public method

Initializes the object.

This method is invoked at the end of the constructor after the object is initialized with the given configuration.

public void init ( )

madd() public method
Deprecated This method is an alias for multiAdd() and will be removed in 2.1.0.

Stores multiple items in cache. Each item contains a value identified by a key.

If the cache already contains such a key, the existing value and expiration time will be preserved.

public array madd ( $items, $duration = 0, $dependency = null )
$items | array | The items to be cached, as key-value pairs.
$duration | integer | Default number of seconds in which the cached values will expire. 0 means never expire.
$dependency | yii\caching\Dependency | Dependency of the cached items. If the dependency changes, the corresponding values in the cache will be invalidated when it is fetched via get(). This parameter is ignored if $serializer is false.
return | array | Array of failed keys

mget() public method
Deprecated This method is an alias for multiGet() and will be removed in 2.1.0.

Retrieves multiple values from cache with the specified keys.

Some caches (such as memcache, apc) allow retrieving multiple cached values at the same time, which may improve the performance. In case a cache does not support this feature natively, this method will try to simulate it.

public array mget ( $keys )
$keys | string[] | List of string 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.

mset() public method
Deprecated This method is an alias for multiSet() and will be removed in 2.1.0.

Stores multiple items in cache. Each item contains a value identified by a key.

If the cache already contains such a key, the existing value and expiration time will be replaced with the new ones, respectively.

public array mset ( $items, $duration = 0, $dependency = null )
$items | array | The items to be cached, as key-value pairs.
$duration | integer | Default number of seconds in which the cached values will expire. 0 means never expire.
$dependency | yii\caching\Dependency | Dependency of the cached items. If the dependency changes, the corresponding values in the cache will be invalidated when it is fetched via get(). This parameter is ignored if $serializer is false.
return | array | Array of failed keys

multiAdd() public method (available since version 2.0.7)

Stores multiple items in cache. Each item contains a value identified by a key.

If the cache already contains such a key, the existing value and expiration time will be preserved.

public array multiAdd ( $items, $duration = 0, $dependency = null )
$items | array | The items to be cached, as key-value pairs.
$duration | integer | Default number of seconds in which the cached values will expire. 0 means never expire.
$dependency | yii\caching\Dependency | Dependency of the cached items. If the dependency changes, the corresponding values in the cache will be invalidated when it is fetched via get(). This parameter is ignored if $serializer is false.
return | array | Array of failed keys

multiGet() public method (available since version 2.0.7)

Retrieves multiple values from cache with the specified keys.

Some caches (such as memcache, apc) allow retrieving multiple cached values at the same time, which may improve the performance. In case a cache does not support this feature natively, this method will try to simulate it.

public array multiGet ( $keys )
$keys | string[] | List of string 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.

multiSet() public method (available since version 2.0.7)

Stores multiple items in cache. Each item contains a value identified by a key.

If the cache already contains such a key, the existing value and expiration time will be replaced with the new ones, respectively.

public array multiSet ( $items, $duration = 0, $dependency = null )
$items | array | The items to be cached, as key-value pairs.
$duration | integer | Default number of seconds in which the cached values will expire. 0 means never expire.
$dependency | yii\caching\Dependency | Dependency of the cached items. If the dependency changes, the corresponding values in the cache will be invalidated when it is fetched via get(). This parameter is ignored if $serializer is false.
return | array | Array of failed keys

offsetExists() public method

Returns whether there is a cache entry with a specified key.

This method is required by the interface ArrayAccess.

public boolean offsetExists ( $key )
$key | string | A key identifying the cached value

offsetGet() public method

Retrieves the value from cache with a specified key.

This method is required by the interface ArrayAccess.

public mixed offsetGet ( $key )
$key | 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.

offsetSet() public method

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.

public void offsetSet ( $key, $value )
$key | string | The key identifying the value to be cached
$value | mixed | The value to be cached

offsetUnset() public method

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

public void offsetUnset ( $key )
$key | string | The key of the value to be deleted

set() public method

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, respectively.

public boolean set ( $key, $value, $duration = null, $dependency = null )
$key | mixed | A key identifying the value to be cached. This can be a simple string or a complex data structure consisting of factors representing the key.
$value | mixed | The value to be cached
$duration | integer | Default duration in seconds before the cache will expire. If not set, default $defaultDuration value is used.
$dependency | yii\caching\Dependency | Dependency of the cached item. If the dependency changes, the corresponding value in the cache will be invalidated when it is fetched via get(). This parameter is ignored if $serializer is false.
return | boolean | Whether the value is successfully stored into cache

setValue() protected abstract method

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.

protected abstract boolean setValue ( $key, $value, $duration )
$key | string | The key identifying the value to be cached
$value | mixed | The value to be cached. Most often it's a string. If you have disabled $serializer, it could be something else.
$duration | 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

setValues() protected method

Stores multiple key-value pairs in cache.

The default implementation calls setValue() multiple times store values one by one. If the underlying cache storage supports multi-set, this method should be overridden to exploit that feature.

protected array setValues ( $data, $duration )
$data | array | Array where key corresponds to cache key while value is the value stored
$duration | integer | The number of seconds in which the cached values will expire. 0 means never expire.
return | array | Array of failed keys