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Core API


The Pool class represents the entire caching system and all of the items in it. Objects of this class are used to retrieve Items from the cache, as well as to perform bulk operations on the system such as Purging or Clearing the cache.



Sets the driver for use by the caching system. This driver handles the direct interface with the caching backends, keeping the system specific development abstracted out.



Sets a PSR LoggerInterface style logging client to enable the tracking of errors.


Places the Pool inside of a "namespace". All Items inside a specific namespace should be completely segmented from all other Items.


Retrieves the current namespace, or false if one isn't set.



The getItem function takes in a key and returns an associated Item object. The structure of keys can be found on the :ref:`basics` page.


getItemIterator(array $keys)

The getItemIterator function takes in an array of keys and returns an Iterator object populated by Item objects for those keys. The structure of keys can be found on the :ref:`basics` page.



The flush function completely empties all items associated with the Pool. After calling this every Item will be considered a miss and will have to be regenerated.



The Purge function allows drivers to perform basic maintenance tasks, such as removing stale or expired items from storage. Not all drivers need this, as many interact with systems that handle that automatically.

It's important that this function is not called from inside a normal request, as the maintenance tasks this allows can occasionally take some time.


The Item class represents specific pieces of data in the caching system. Item objects are created by the Pool class.


get($invalidation == Invalidation::PRECOMPUTE, [$args])

Retrieves the stored value of the Item or null if one is not set. Because null can be a valid stored object it is important to call isMiss in order to actually check it's validity.

The get function can take a series of optional arguments defining how it handles cache misses. The first of these options is the invalidation method to be used, while the other options all provide invalidation specific options. The :ref:`invalidation` page contains much more information about hos to use this functionality.



The isMiss function returns true when the current Item has either stale or no data. Since Stash is capable of storing both null and false values and returning them via the get function this is the only real way to test whether a cached value is usable or not.

The exact behavior used to define a cache miss is defined by the invalidation method used for the object. The :ref:`invalidation` page contains much more information about hos to use this functionality.


lock($ttl = null)

This should be called right before the script attempts to regenerate data from a cache miss. It signifies to other processes or requests that the data is being generated and allows them to take special action to improve system performance. Put more simply, just call this function and your cache will be higher performing as a result.

The exact effect of this function depends on which invalidation method is being used. The :ref:`invalidation` page contains much more information about how to use this functionality.


set($data, $ttl = null)

The set function is used to populate the cache with data. The first argument can be any type of data that is able to be serialized- essentially everything except resources and classes which can't be serialized.

The second argument defines how long the Item will be stored in the cache. This is a maximum time, as Items can be cleared or removed earlier but will never be considered a cache hit after it. This argument can either be a DateTime defining a specific expiration or an integer representing the time, in seconds, that the data should be considered fresh.



The clear function removes the current Item's data from the backend storage.

If hierarchical or "stackable" caching is being used this function will also remove children Items. The Key section of the :ref:`basics` document goes into more detail about how that works.


extend($ttl = null)

This extends the Item's lifetime without changing it's data. Like the set function, the ttl can be a DateTime or integer.



The getKey function returns this Item's key as a string. This is particularly useful when the Item is returned as a group of Items in an Iterator.



This returns a DateTime of the Item's creation time, if it is available.



This returns a DateTime of the Item's expiration time, if it is available.



The disable function prevents any read or write operations and forces all the other calls to fail gracefully.


Stash works by storing values into various backend systems, like APC and Memcached, and retrieving them later. With the exception their creation and setup, drivers don't have any "public" functions- they are used by the Pool and Item classes themselves to interact with the underlying cache system.

The :ref:`Drivers` page contains a list of all drivers and their options.


setOptions(array $options)

Passes an array of options to the Driver. This can include things like server addresses or directories to use for cache storage.


The DriverList class contains functions that are useful for people integrating or extending Stash. It primarily provides information on what Drivers are available.



Returns an associative array, $name => $class, of Drivers that can be enabled on this system.



Returns an associative array, $name => $class, of all Drivers regardless of whether they can run on this system.



Returns the class name of the requested driver.


DriverList::registerDriver($name, $class)

Adds a new Driver to the list of system drivers. This is used for extending Stash with custom drivers.