Drupal 8  8.0.2
BackendChain Class Reference
Inheritance diagram for BackendChain:

Public Member Functions

 __construct ($bin)
 
 appendBackend (CacheBackendInterface $backend)
 
 prependBackend (CacheBackendInterface $backend)
 
 get ($cid, $allow_invalid=FALSE)
 
 getMultiple (&$cids, $allow_invalid=FALSE)
 
 set ($cid, $data, $expire=Cache::PERMANENT, array $tags=array())
 
 setMultiple (array $items)
 
 delete ($cid)
 
 deleteMultiple (array $cids)
 
 deleteAll ()
 
 invalidate ($cid)
 
 invalidateMultiple (array $cids)
 
 invalidateTags (array $tags)
 
 invalidateAll ()
 
 garbageCollection ()
 
 removeBin ()
 

Protected Attributes

 $backends = array()
 

Additional Inherited Members

- Data Fields inherited from CacheBackendInterface
const CACHE_PERMANENT = -1
 

Detailed Description

Defines a chained cache implementation for combining multiple cache backends.

Can be used to combine two or more backends together to behave as if they were a single backend.

For example a slower, persistent storage engine could be combined with a faster, volatile storage engine. When retrieving items from cache, they will be fetched from the volatile backend first, only falling back to the persistent backend if an item is not available. An item not present in the volatile backend but found in the persistent one will be propagated back up to ensure fast retrieval on the next request. On cache sets and deletes, both backends will be invoked to ensure consistency.

See Also

Constructor & Destructor Documentation

__construct (   $bin)

Constructs a DatabaseBackend object.

Parameters
string$binThe cache bin for which the object is created.

Member Function Documentation

appendBackend ( CacheBackendInterface  $backend)

Appends a cache backend to the cache chain.

Parameters
CacheBackendInterface$backendThe cache backend to be appended to the cache chain.
Returns
The called object.
delete (   $cid)

{Deletes an item from the cache.If the cache item is being deleted because it is no longer "fresh", you may consider using invalidate() instead. This allows callers to retrieve the invalid item by calling get() with $allow_invalid set to TRUE. In some cases an invalid item may be acceptable rather than having to rebuild the cache.

Parameters
string$cidThe cache ID to delete.
See Also
::invalidate()
::deleteMultiple()
::deleteAll()
}

Implements CacheBackendInterface.

deleteAll ( )

{Deletes all cache items in a bin.

See Also
::invalidateAll()
::delete()
::deleteMultiple()
}

Implements CacheBackendInterface.

deleteMultiple ( array  $cids)

{Deletes multiple items from the cache.If the cache items are being deleted because they are no longer "fresh", you may consider using invalidateMultiple() instead. This allows callers to retrieve the invalid items by calling get() with $allow_invalid set to TRUE. In some cases an invalid item may be acceptable rather than having to rebuild the cache.

Parameters
array$cidsAn array of cache IDs to delete.
See Also
::invalidateMultiple()
::delete()
::deleteAll()
}

Implements CacheBackendInterface.

garbageCollection ( )

{Performs garbage collection on a cache bin.The backend may choose to delete expired or invalidated items.}

Implements CacheBackendInterface.

get (   $cid,
  $allow_invalid = FALSE 
)

{Returns data from the persistent cache.

Parameters
string$cidThe cache ID of the data to retrieve.
bool$allow_invalid(optional) If TRUE, a cache item may be returned even if it is expired or has been invalidated. Such items may sometimes be preferred, if the alternative is recalculating the value stored in the cache, especially if another concurrent request is already recalculating the same value. The "valid" property of the returned object indicates whether the item is valid or not. Defaults to FALSE.
Returns
object|false The cache item or FALSE on failure.
See Also
::getMultiple()
}

Implements CacheBackendInterface.

getMultiple ( $cids,
  $allow_invalid = FALSE 
)

{Returns data from the persistent cache when given an array of cache IDs.

Parameters
array$cidsAn array of cache IDs for the data to retrieve. This is passed by reference, and will have the IDs successfully returned from cache removed.
bool$allow_invalid(optional) If TRUE, cache items may be returned even if they have expired or been invalidated. Such items may sometimes be preferred, if the alternative is recalculating the value stored in the cache, especially if another concurrent thread is already recalculating the same value. The "valid" property of the returned objects indicates whether the items are valid or not. Defaults to FALSE.
Returns
array An array of cache item objects indexed by cache ID.
See Also
::get()
}

Implements CacheBackendInterface.

invalidate (   $cid)

{Marks a cache item as invalid.Invalid items may be returned in later calls to get(), if the $allow_invalid argument is TRUE.

Parameters
string$cidThe cache ID to invalidate.
See Also
::delete()
::invalidateMultiple()
::invalidateAll()
}

Implements CacheBackendInterface.

invalidateAll ( )

{Marks all cache items as invalid.Invalid items may be returned in later calls to get(), if the $allow_invalid argument is TRUE.

See Also
::deleteAll()
::invalidate()
::invalidateMultiple()
}

Implements CacheBackendInterface.

invalidateMultiple ( array  $cids)

{Marks cache items as invalid.Invalid items may be returned in later calls to get(), if the $allow_invalid argument is TRUE.

Parameters
string[]$cids An array of cache IDs to invalidate.
See Also
::deleteMultiple()
::invalidate()
::invalidateAll()
}

Implements CacheBackendInterface.

invalidateTags ( array  $tags)

{Marks cache items with any of the specified tags as invalid.

Parameters
string[]$tags The list of tags for which to invalidate cache items.
}

Implements CacheTagsInvalidatorInterface.

prependBackend ( CacheBackendInterface  $backend)

Prepends a cache backend to the cache chain.

Parameters
CacheBackendInterface$backendThe backend to be prepended to the cache chain.
Returns
The called object.
removeBin ( )

{Remove a cache bin.}

Implements CacheBackendInterface.

set (   $cid,
  $data,
  $expire = Cache::PERMANENT,
array  $tags = array() 
)

{Stores data in the persistent cache.Core cache implementations set the created time on cache item with microtime(TRUE) rather than REQUEST_TIME_FLOAT, because the created time of cache items should match when they are created, not when the request started. Apart from being more accurate, this increases the chance an item will legitimately be considered valid.

Parameters
string$cidThe cache ID of the data to store.
mixed$dataThe data to store in the cache. Some storage engines only allow objects up to a maximum of 1MB in size to be stored by default. When caching large arrays or similar, take care to ensure $data does not exceed this size.
int$expireOne of the following values:
  • CacheBackendInterface::CACHE_PERMANENT: Indicates that the item should not be removed unless it is deleted explicitly.
  • A Unix timestamp: Indicates that the item will be considered invalid after this time, i.e. it will not be returned by get() unless $allow_invalid has been set to TRUE. When the item has expired, it may be permanently deleted by the garbage collector at any time.
array$tagsAn array of tags to be stored with the cache item. These should normally identify objects used to build the cache item, which should trigger cache invalidation when updated. For example if a cached item represents a node, both the node ID and the author's user ID might be passed in as tags. For example array('node' => array(123), 'user' => array(92)).
See Also
::get()
::getMultiple()
}

Implements CacheBackendInterface.

setMultiple ( array  $items)

{Store multiple items in the persistent cache.

Parameters
array$itemsAn array of cache items, keyed by cid. In the form:
$items = array(
$cid => array(
// Required, will be automatically serialized if not a string.
'data' => $data,
// Optional, defaults to CacheBackendInterface::CACHE_PERMANENT.
// (optional) The cache tags for this item, see CacheBackendInterface::set().
'tags' => array(),
),
);
}

Implements CacheBackendInterface.


The documentation for this class was generated from the following file: