1. class
  2. Drupal
  3. \
  4. Core
  5. \
  6. Cache
  7. \
  8. NullBackend

NullBackend

class NullBackend implements CacheBackendInterface (View source)

Defines a stub cache implementation.

The stub implementation is needed when database access is not yet available. Because Drupal's caching system never requires that cached data be present, these stub functions can short-circuit the process and sidestep the need for any persistent storage. Using this cache implementation during normal operations would have a negative impact on performance.

This also can be used for testing purposes.

Methods

__construct(string $bin)

Constructs a NullBackend object.

object|false
get(string $cid, bool $allow_invalid = FALSE)

Returns data from the persistent cache.

array
getMultiple(array $cids, bool $allow_invalid = FALSE)

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

set(string $cid, mixed $data, int $expire = Cache::PERMANENT, array $tags = [])

Stores data in the persistent cache.

setMultiple(array $items = [])

Store multiple items in the persistent cache.

delete(string $cid)

Deletes an item from the cache.

deleteMultiple(array $cids)

Deletes multiple items from the cache.

deleteAll()

Deletes all cache items in a bin.

invalidate(string $cid)

Marks a cache item as invalid.

invalidateMultiple(array $cids)

Marks cache items as invalid.

invalidateAll()

Marks all cache items as invalid.

garbageCollection()

Performs garbage collection on a cache bin.

removeBin()

Remove a cache bin.

Details

at line 26
__construct(string $bin)

Constructs a NullBackend object.

Parameters

string $bin

The cache bin for which the object is created.

at line 31
object|false get(string $cid, bool $allow_invalid = FALSE)

Returns data from the persistent cache.

Parameters

string $cid

The 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.

Return Value

object|false

The cache item or FALSE on failure.

at line 38
array getMultiple(array $cids, bool $allow_invalid = FALSE)

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

Parameters

array $cids

An 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.

Return Value

array

An array of cache item objects indexed by cache ID.

at line 45
set(string $cid, mixed $data, int $expire = Cache::PERMANENT, array $tags = [])

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 $cid

The cache ID of the data to store.
mixed $data

The 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 $expire

One 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 $tags

An 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 ['node:123', 'node:456', 'user:789'].

at line 50
setMultiple(array $items = [])

Store multiple items in the persistent cache.

Parameters

array $items

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

at line 55
delete(string $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 $cid

The cache ID to delete.

at line 60
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 $cids

An array of cache IDs to delete.

at line 65
deleteAll()

Deletes all cache items in a bin.

at line 70
invalidate(string $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 $cid

The cache ID to invalidate.

at line 75
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

array $cids

An array of cache IDs to invalidate.

at line 80
invalidateAll()

Marks all cache items as invalid.

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

at line 85
garbageCollection()

Performs garbage collection on a cache bin.

The backend may choose to delete expired or invalidated items.

at line 90
removeBin()

Remove a cache bin.