# phpman > perldoc > Cache::Cache ## NAME [Cache::Cache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ACache/markdown) -- the Cache interface. ## DESCRIPTION The Cache modules are designed to assist a developer in persisting data for a specified period of time. Often these modules are used in web applications to store data locally to save repeated and redundant expensive calls to remote machines or databases. People have also been known to use [Cache::Cache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ACache/markdown) for its straightforward interface in sharing data between runs of an application or invocations of a CGI-style script or simply as an easy to use abstraction of the filesystem or shared memory. The [Cache::Cache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ACache/markdown) interface is implemented by classes that support the get, set, remove, size, purge, and clear instance methods and their corresponding static methods for persisting data across method calls. [CACHE::CACHE](https://www.chedong.com/phpMan.php/perldoc/CACHE%3A%3ACACHE/markdown) VERSUS CHI [Cache::Cache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ACache/markdown) is in wide use and very stable, but has not changed in years and is no longer actively developed. CHI is the successor to [Cache::Cache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ACache/markdown). It adheres to the basic [Cache::Cache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ACache/markdown) API but adds new features and drivers (e.g. FastMmap and Memcached), improves performance, and addresses limitations in the [Cache::Cache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ACache/markdown) implementation. The authors recommend the use of CHI going forward. Questions about [Cache::Cache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ACache/markdown) and CHI may be directed to the perl-cache mailing list at . ## USAGE First, choose the best type of cache implementation for your needs. The simplest cache is the MemoryCache, which is suitable for applications that are serving multiple sequential requests, and wish to avoid making redundant expensive queries, such as an Apache/mod_perl application talking to a database. If you wish to share that data between processes, then perhaps the SharedMemoryCache is appropriate, although its behavior is tightly bound to the underlying IPC mechanism, which varies from system to system, and is unsuitable for large objects or large numbers of objects. When the SharedMemoryCache is not acceptable, then FileCache offers all of the same functionality with similar performance metrics, and it is not limited in terms of the number of objects or their size. If you wish to maintain a strict limit on the size of a file system based cache, then the SizeAwareFileCache is the way to go. Similarly, the SizeAwareMemoryCache and the SizeAwareSharedMemoryCache add size management functionality to the MemoryCache and SharedMemoryCache classes respectively. Using a cache is simple. Here is some sample code for instantiating and using a file system based cache. use [Cache::FileCache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3AFileCache/markdown); my $cache = new [Cache::FileCache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3AFileCache/markdown)( ); my $customer = $cache->get( $name ); if ( not defined $customer ) { $customer = get_customer_from_db( $name ); $cache->set( $name, $customer, "10 minutes" ); } return $customer; ## CONSTANTS *$EXPIRES_NEVER* The item being set in the cache will never expire. *$EXPIRES_NOW* The item being set in the cache will expire immediately. ## METHODS Clear( ) Remove all objects from all caches of this type. Purge( ) Remove all objects that have expired from all caches of this type. Size( ) Returns the total size of all objects in all caches of this type. ### new Construct a new instance of a [Cache::Cache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ACache/markdown). *$options_hash_ref* is a reference to a hash containing configuration options; see the section OPTIONS below. ### clear Remove all objects from the namespace associated with this cache instance. ### get Returns the data associated with *$key*. ### get_object Returns the underlying [Cache::Object](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3AObject/markdown) object used to store the cached data associated with *$key*. This will not trigger a removal of the cached object even if the object has expired. ### purge Remove all objects that have expired from the namespace associated with this cache instance. ### remove Delete the data associated with the *$key* from the cache. ### set Associates *$data* with *$key* in the cache. *$expires_in* indicates the time in seconds until this data should be erased, or the constant $EXPIRES_NOW, or the constant $EXPIRES_NEVER. Defaults to $EXPIRES_NEVER. This variable can also be in the extended format of "[number] [unit]", e.g., "10 minutes". The valid units are s, second, seconds, sec, m, minute, minutes, min, h, hour, hours, d, day, days, w, week, weeks, M, month, months, y, year, and years. Additionally, $EXPIRES_NOW can be represented as "now" and $EXPIRES_NEVER can be represented as "never". ### set_object Associates *$key* with [Cache::Object](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3AObject/markdown) *$object*. Using set_object (as opposed to set) does not trigger an automatic removal of expired objects. ### size Returns the total size of all objects in the namespace associated with this cache instance. ### get_namespaces Returns all the namespaces associated with this type of cache. ## OPTIONS The options are set by passing in a reference to a hash containing any of the following keys: *namespace* The namespace associated with this cache. Defaults to "Default" if not explicitly set. *default_expires_in* The default expiration time for objects place in the cache. Defaults to $EXPIRES_NEVER if not explicitly set. *auto_purge_interval* Sets the auto purge interval. If this option is set to a particular time ( in the same format as the expires_in ), then the purge( ) routine will be called during the first set after the interval expires. The interval will then be reset. *auto_purge_on_set* If this option is true, then the auto purge interval routine will be checked on every set. *auto_purge_on_get* If this option is true, then the auto purge interval routine will be checked on every get. ## PROPERTIES (get|set)_namespace( ) The namespace of this cache instance ### get_default_expires_in The default expiration time for objects placed in this cache instance ### get_keys The list of keys specifying objects in the namespace associated with this cache instance ### get_identifiers This method has been deprecated in favor of get_keys( ). (get|set)_auto_purge_interval( ) Accesses the auto purge interval. If this option is set to a particular time ( in the same format as the expires_in ), then the purge( ) routine will be called during the first get after the interval expires. The interval will then be reset. (get|set)_auto_purge_on_set( ) If this property is true, then the auto purge interval routine will be checked on every set. (get|set)_auto_purge_on_get( ) If this property is true, then the auto purge interval routine will be checked on every get. ## SEE ALSO CHI - the successor to [Cache::Cache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ACache/markdown) [Cache::Object](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3AObject/markdown), [Cache::MemoryCache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3AMemoryCache/markdown), [Cache::FileCache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3AFileCache/markdown), [Cache::SharedMemoryCache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ASharedMemoryCache/markdown), and [Cache::SizeAwareFileCache](https://www.chedong.com/phpMan.php/perldoc/Cache%3A%3ASizeAwareFileCache/markdown) ## AUTHOR Original author: DeWitt Clinton <> Last author: $Author: dclinton $ Copyright (C) 2001-2003 DeWitt Clinton