PHP Class WP_Object_Cache, wp-redis

The WordPress Object Cache is used to save on trips to the database. The Object Cache stores all of the cache data to memory and makes the cache contents available by using a key, which is used to name and later retrieve the cache contents. The Object Cache can be replaced by other caching mechanisms by placing files in the wp-content folder which is looked at in wp-settings. If that file exists, then this file will not be included.

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Public Properties

Property	Type	Description
$blog_prefix	integer	The blog prefix to prepend to keys in non-global groups.
$cache	array	Holds the cached objects
$cache_hits	integer	The amount of times the cache data was already stored in the cache.
$cache_misses	integer	Amount of times the cache did not have the request in cache
$do_redis_failback_flush	boolean	Whether or not the object cache thinks Redis needs a flush
$global_groups	array	List of global groups
$is_redis_connected	boolean	Whether or not Redis is connected
$last_triggered_error		The last triggered error
$non_persistent_groups	array	List of non-persistent groups
$redis_calls	integer	The amount of times a request was made to Redis
$redis_hash_groups	array	List of groups which use Redis hashes.

Public Methods

Method	Description
__construct ( ) : null \| WP_Object_Cache	Sets up object properties; PHP 5 style constructor
__destruct ( ) : boolean	Will save the object cache before object is completely destroyed.
add ( integer \| string $key, mixed $data, string $group = 'default', integer $expire ) : boolean	Adds data to the cache if it doesn't already exist.
add_global_groups ( array $groups )	Sets the list of global groups.
add_non_persistent_groups ( array $groups )	Sets the list of non-persistent groups.
add_redis_hash_groups ( array $groups )	Sets the list of groups that use Redis hashes.
decr ( integer \| string $key, integer $offset = 1, string $group = 'default' ) : false \| integer	Decrement numeric cache item's value
delete ( integer \| string $key, string $group = 'default', boolean $force = false ) : boolean	Remove the contents of the cache key in the group
delete_group ( string $group ) : boolean	Remove the contents of all cache keys in the group.
flush ( boolean $redis = true ) : boolean	Clears the object cache of all data.
get ( integer \| string $key, string $group = 'default', string $force = false, boolean &$found = null ) : boolean \| mixed	Retrieves the cache contents, if it exists
incr ( integer \| string $key, integer $offset = 1, string $group = 'default' ) : false \| integer	Increment numeric cache item's value
replace ( integer \| string $key, mixed $data, string $group = 'default', integer $expire ) : boolean	Replace the contents in the cache, if contents already exist
reset ( )	Reset keys
set ( integer \| string $key, mixed $data, string $group = 'default', integer $expire ) : boolean	Sets the data contents into the cache
stats ( )	Echoes the stats of the caching.
switch_to_blog ( integer $blog_id )	Switch the interal blog id.
wp_action_admin_notices_warn_missing_redis ( )	Admin UI to let the end user know something about the Redis connection isn't working.

Protected Methods

Method	Description
_call_redis ( string $method ) : mixed	Wrapper method for calls to Redis, which fails gracefully when Redis is unavailable
_connect_redis ( )	Wrapper method for connecting to Redis, which lets us retry the connection
_exists ( $key, $group )	Utility function to determine whether a key exists in the cache.
_get_internal ( string $key, string $group ) : mixed	Get a value from the internal object cache
_isset_internal ( string $key, string $group ) : boolean	Check whether there's a value in the internal object cache.
_key ( string $key = '', string $group = 'default' ) : string	Utility function to generate the redis key for a given key and group.
_set_internal ( string $key, string $group, mixed $value )	Set a value to the internal object cache
_should_persist ( string $group ) : boolean	Does this group use persistent storage?
_should_use_redis_hashes ( string $group ) : boolean	Should this group use Redis hashes?
_unset_internal ( string $key, string $group )	Unset a value from the internal object cache

Private Methods

Method	Description
is_redis_failback_flush_enabled ( ) : boolean	Whether or not wakeup flush is enabled

Method Details

__construct() public method

Sets up object properties; PHP 5 style constructor

public __construct ( ) : null \| WP_Object_Cache
return	null \| WP_Object_Cache	If cache is disabled, returns null.

__destruct() public method

Called upon object destruction, which should be when PHP ends.

public __destruct ( ) : boolean
return	boolean	True value. Won't be used by PHP

_call_redis() protected method

Wrapper method for calls to Redis, which fails gracefully when Redis is unavailable

protected _call_redis ( string $method ) : mixed
$method	string
return	mixed

_connect_redis() protected method

Wrapper method for connecting to Redis, which lets us retry the connection

protected _connect_redis ( )

_exists() protected method

Utility function to determine whether a key exists in the cache.

protected _exists ( $key, $group )

_get_internal() protected method

Get a value from the internal object cache

protected _get_internal ( string $key, string $group ) : mixed
$key	string
$group	string
return	mixed

_isset_internal() protected method

Check whether there's a value in the internal object cache.

protected _isset_internal ( string $key, string $group ) : boolean
$key	string
$group	string
return	boolean

_key() protected method

Utility function to generate the redis key for a given key and group.

protected _key ( string $key = '', string $group = 'default' ) : string
$key	string	The cache key.
$group	string	The cache group.
return	string	A properly prefixed redis cache key.

_set_internal() protected method

Set a value to the internal object cache

protected _set_internal ( string $key, string $group, mixed $value )
$key	string
$group	string
$value	mixed

_should_persist() protected method

Does this group use persistent storage?

protected _should_persist ( string $group ) : boolean
$group	string	Cache group.
return	boolean	true if the group is persistent, false if not.

_should_use_redis_hashes() protected method

Should this group use Redis hashes?

protected _should_use_redis_hashes ( string $group ) : boolean
$group	string	Cache group.
return	boolean	True if the group should use Redis hashes, false if not.

_unset_internal() protected method

Unset a value from the internal object cache

protected _unset_internal ( string $key, string $group )
$key	string
$group	string

add() public method

Adds data to the cache if it doesn't already exist.

public add ( integer \| string $key, mixed $data, string $group = 'default', integer $expire ) : boolean
$key	integer \| string	What to call the contents in the cache
$data	mixed	The contents to store in the cache
$group	string	Where to group the cache contents
$expire	integer	When to expire the cache contents
return	boolean	False if cache key and group already exist, true on success

add_global_groups() public method

Sets the list of global groups.

public add_global_groups ( array $groups )
$groups	array	List of groups that are global.

add_non_persistent_groups() public method

Sets the list of non-persistent groups.

public add_non_persistent_groups ( array $groups )
$groups	array	List of groups that are non-persistent.

add_redis_hash_groups() public method

Sets the list of groups that use Redis hashes.

public add_redis_hash_groups ( array $groups )
$groups	array	List of groups that use Redis hashes.

decr() public method

Decrement numeric cache item's value

public decr ( integer \| string $key, integer $offset = 1, string $group = 'default' ) : false \| integer
$key	integer \| string	The cache key to increment
$offset	integer	The amount by which to decrement the item's value. Default is 1.
$group	string	The group the key is in.
return	false \| integer	False on failure, the item's new value on success.

delete() public method

If the cache key does not exist in the group and $force parameter is set to false, then nothing will happen. The $force parameter is set to false by default.

public delete ( integer \| string $key, string $group = 'default', boolean $force = false ) : boolean
$key	integer \| string	What the contents in the cache are called
$group	string	Where the cache contents are grouped
$force	boolean	Optional. Whether to force the unsetting of the cache key in the group
return	boolean	False if the contents weren't deleted and true on success

delete_group() public method

Remove the contents of all cache keys in the group.

public delete_group ( string $group ) : boolean
$group	string	Where the cache contents are grouped.
return	boolean	True on success, false on failure.

flush() public method

By default, this will flush the session cache as well as Redis, but we can leave the redis cache intact if we want. This is helpful when, for instance, you're running a batch process and want to clear the session store to reduce the memory footprint, but you don't want to have to re-fetch all the values from the database.

public flush ( boolean $redis = true ) : boolean
$redis	boolean	Should we flush redis as well as the session cache?
return	boolean	Always returns true

get() public method

The contents will be first attempted to be retrieved by searching by the key in the cache group. If the cache is hit (success) then the contents are returned. On failure, the number of cache misses will be incremented.

public get ( integer \| string $key, string $group = 'default', string $force = false, boolean &$found = null ) : boolean \| mixed
$key	integer \| string	What the contents in the cache are called
$group	string	Where the cache contents are grouped
$force	string	Whether to force a refetch rather than relying on the local cache (default is false)
$found	boolean	Optional. Whether the key was found in the cache. Disambiguates a return of false, a storable value. Passed by reference. Default null.
return	boolean \| mixed	False on failure to retrieve contents or the cache contents on success

incr() public method

Increment numeric cache item's value

public incr ( integer \| string $key, integer $offset = 1, string $group = 'default' ) : false \| integer
$key	integer \| string	The cache key to increment
$offset	integer	The amount by which to increment the item's value. Default is 1.
$group	string	The group the key is in.
return	false \| integer	False on failure, the item's new value on success.

replace() public method

Replace the contents in the cache, if contents already exist

reset() public method

Reset keys

Deprecation: 3.5.0

public reset ( )

set() public method

The cache contents is grouped by the $group parameter followed by the $key. This allows for duplicate ids in unique groups. Therefore, naming of the group should be used with care and should follow normal function naming guidelines outside of core WordPress usage. The $expire parameter is not used, because the cache will automatically expire for each time a page is accessed and PHP finishes. The method is more for cache plugins which use files.

public set ( integer \| string $key, mixed $data, string $group = 'default', integer $expire ) : boolean
$key	integer \| string	What to call the contents in the cache
$data	mixed	The contents to store in the cache
$group	string	Where to group the cache contents
$expire	integer	TTL for the data, in seconds
return	boolean	Always returns true

stats() public method

Gives the cache hits, and cache misses. Also prints every cached group, key and the data.

public stats ( )

switch_to_blog() public method

This changes the blog id used to create keys in blog specific groups.

public switch_to_blog ( integer $blog_id )
$blog_id	integer	Blog ID

wp_action_admin_notices_warn_missing_redis() public method

Admin UI to let the end user know something about the Redis connection isn't working.

public wp_action_admin_notices_warn_missing_redis ( )

Property Details

$blog_prefix public_oe property

The blog prefix to prepend to keys in non-global groups.

public int $blog_prefix
return	integer

$cache public_oe property

Holds the cached objects

public array $cache
return	array

$cache_hits public_oe property

The amount of times the cache data was already stored in the cache.

public int $cache_hits
return	integer

$cache_misses public_oe property

Amount of times the cache did not have the request in cache

public int $cache_misses
return	integer

$do_redis_failback_flush public_oe property

Whether or not the object cache thinks Redis needs a flush

public bool $do_redis_failback_flush
return	boolean

$global_groups public_oe property

List of global groups

public array $global_groups
return	array

$is_redis_connected public_oe property

Whether or not Redis is connected

public bool $is_redis_connected
return	boolean

$last_triggered_error public_oe property

The last triggered error

public $last_triggered_error

$non_persistent_groups public_oe property

List of non-persistent groups

public array $non_persistent_groups
return	array

$redis_calls public_oe property

The amount of times a request was made to Redis

public int $redis_calls
return	integer

$redis_hash_groups public_oe property

List of groups which use Redis hashes.

public array $redis_hash_groups
return	array

public replace ( integer \| string $key, mixed $data, string $group = 'default', integer $expire ) : boolean
$key	integer \| string	What to call the contents in the cache
$data	mixed	The contents to store in the cache
$group	string	Where to group the cache contents
$expire	integer	When to expire the cache contents
return	boolean	False if not exists, true if contents were replaced