6.4. Zend_Cache Backends

There are two kinds of backends: standard ones and extended ones. Of course, extended backends offer more features.

6.4.1. Zend_Cache_Backend_File

This (extended) backends stores cache records into files (in a choosen directory).

Available options are :

Table 6.6. File Backend Options

Option Data Type Default Value Description
cache_dir String '/tmp/' Directory where to store cache files
file_locking Boolean TRUE Enable / disable file_locking : Can avoid cache corruption under bad circumstances but it doesn't help on multithread webservers or on NFS filesystems...
read_control Boolean TRUE Enable / disable read control : if enabled, a control key is embedded in the cache file and this key is compared with the one calculated after the reading.
read_control_type String 'crc32' Type of read control (only if read control is enabled). Available values are : 'md5' (best but slowest), 'crc32' (lightly less safe but faster, better choice), 'adler32' (new choice, faster than crc32), 'strlen' for a length only test (fastest).
hashed_directory_level Integer 0 Hashed directory structure level : 0 means "no hashed directory structure", 1 means "one level of directory", 2 means "two levels"... This option can speed up the cache only when you have many thousands of cache files. Only specific benchs can help you to choose the perfect value for you. Maybe, 1 or 2 is a good start.
hashed_directory_umask Integer 0700 Umask for the hashed directory structure
file_name_prefix String 'zend_cache' prefix for cache files ; be really careful with this option because a too generic value in a system cache dir (like /tmp) can cause disasters when cleaning the cache
cache_file_umask Integer 0700 umask for cache files
metatadatas_array_max_size Integer 100 internal max size for the metadatas array (don't change this value unless you know what you are doing)

6.4.2. Zend_Cache_Backend_Sqlite

This (extended) backends stores cache records into a SQLite database.

Available options are :

Table 6.7. Sqlite Backend Options

Option Data Type Default Value Description
cache_db_complete_path (mandatory) String NULL The complete path (filename included) of the SQLite database
automatic_vacuum_factor Integer 10 Disable / Tune the automatic vacuum process. The automatic vacuum process defragment the database file (and make it smaller) when a clean() or delete() is called : 0 means no automatic vacuum ; 1 means systematic vacuum (when delete() or clean() methods are called) ; x (integer) > 1 => automatic vacuum randomly 1 times on x clean() or delete().

6.4.3. Zend_Cache_Backend_Memcached

This (extended) backends stores cache records into a memcached server. memcached is a high-performance, distributed memory object caching system. To use this backend, you need a memcached daemon and the memcache PECL extension.

Be careful : with this backend, "tags" are not supported for the moment as the "doNotTestCacheValidity=true" argument.

Available options are :

Table 6.8. Memcached Backend Options

Option Data Type Default Value Description
servers Array array(array('host' => 'localhost', 'port' => 11211, 'persistent' => true, 'weight' => 1, 'timeout' => 5, 'retry_interval' => 15, 'status' => true, 'failure_callback' => '' )) An array of memcached servers ; each memcached server is described by an associative array : 'host' => (string) : the name of the memcached server, 'port' => (int) : the port of the memcached server, 'persistent' => (bool) : use or not persistent connections to this memcached server 'weight' => (int) :the weight of the memcached server, 'timeout' => (int) :the time out of the memcached server, 'retry_interval' => (int) :the retry interval of the memcached server, 'status' => (bool) :the status of the memcached server, 'failure_callback' => (callback) : the failure_callback of the memcached server
compression Boolean FALSE true if you want to use on-the-fly compression
compatibility Boolean FALSE true if you want to use this compatibility mode with old memcache servers/extensions

6.4.4. Zend_Cache_Backend_Apc

This (extended) backends stores cache records in shared memory through the APC (Alternative PHP Cache) extension (which is of course need for using this backend).

Be careful : with this backend, "tags" are not supported for the moment as the "doNotTestCacheValidity=true" argument.

There is no option for this backend.

6.4.5. Zend_Cache_Backend_Xcache

This backends stores cache records in shared memory through the XCache extension (which is of course need for using this backend).

Be careful : with this backend, "tags" are not supported for the moment as the "doNotTestCacheValidity=true" argument.

Available options are :

Table 6.9. Xcache Backend Options

Option Data Type Default Value Description
user String NULL xcache.admin.user, necessary for the clean() method
password String NULL xcache.admin.pass (in clear form, not MD5), necessary for the clean() method

6.4.6. Zend_Cache_Backend_ZendPlatform

This backend uses content caching API of the Zend Platform product. Naturally, to use this backend you need to have Zend Platform installed.

This backend supports tags, but does not support CLEANING_MODE_NOT_MATCHING_TAG cleaning mode.

Specify this backend using a word separator -- '-', '.', ' ', or '_' -- between the words 'Zend' and 'Platform' when using the Zend_Cache::factory() method:

$cache = Zend_Cache::factory('Core', 'Zend Platform');

There are no options for this backend.

6.4.7. Zend_Cache_Backend_TwoLevels

This (extend) backend is an hybrid one. It stores cache records in two other backends : a fast one (but limited) like Apc, Memcache... and a "slow" one like File, Sqlite...

This backend will use the priority parameter (given at the frontend level when storing a record) and the remaining space in the fast backend to optimize the usage of these two backends. FIXME

Available options are :

Table 6.10. TwoLevels Backend Options

Option Data Type Default Value Description
slow_backend String File the "slow" backend name
fast_backend String Apc the "fast" backend name
slow_backend_options Array array() the "slow" backend options
fast_backend_options Array array() the "fast" backend options
slow_backend_custom_naming Boolean FALSE if true, the slow_backend argument is used as a complete class name ; if false, the frontend argument is used as the end of "Zend_Cache_Backend_[...]" class name
fast_backend_custom_naming Boolean FALSE if true, the fast_backend argument is used as a complete class name ; if false, the frontend argument is used as the end of "Zend_Cache_Backend_[...]" class name
slow_backend_autoload Boolean FALSE if true, there will no require_once for the slow backend (useful only for custom backends)
fast_backend_autoload Boolean FALSE if true, there will no require_once for the fast backend (useful only for custom backends)
auto_refresh_fast_cache Boolean TRUE if true, auto refresh the fast cache when a cache record is hit
stats_update_factor Integer 10 disable / tune the computation of the fast backend filling percentage (when saving a record into cache, computation of the fast backend filling percentage randomly 1 times on x cache writes)

6.4.8. Zend_Cache_Backend_ZendServer_Disk and Zend_Cache_Backend_ZendServer_ShMem

These backends store cache records using Zend Server caching functionality.

Be careful: with these backends, "tags" are not supported for the moment as the "doNotTestCacheValidity=true" argument.

These backend work only withing Zend Server environment for pages requested through HTTP(S) and don't work for command line script execution

There is no option for this backend.