# Developer Information¶

This chapter is targeted at extension authors who want to use the caching framework for their needs. It is about how to use the framework properly. For details about its inner working, please refer to the section about architecture.

Example usages can be found throughout the TYPO3 CMS Core, in particular in system extension core and extbase.

## Cache Registration¶

Registration of a new cache should be done in ext_localconf.php. The example below just defines an empty sub-array in cacheConfigurations. Neither frontend nor backend are defined, meaning that the cache manager will choose the default variable frontend and the database backend by default.

$GLOBALS['TYPO3_CONF_VARS']['SYS']['caching']['cacheConfigurations']['myext_mycache'] ??= [];  Tip The null coalescing assignment operator (??=) check is used to enable administrators to overwrite configuration of caches in LocalConfiguration.php. During bootstrap, any ext_localconf.php is loaded after DefaultConfiguration.php and AdditionalConfiguration.php are loaded, so it is important to make sure that the administrator did not already set any configuration of the extensions cache. If special settings are needed, for example a specific backend (like the transient memory backend), it can be defined with an additional line below the cache array declaration. The extension documentation should hint an integrator about specific caching needs or setups in this case. Tip Extensions should not force specific settings, therefore the null coalescing assignment operator (??=) is used to allow administrators to overwrite those settings. It is recommended to set up a cache configuration with sane defaults, but administrators should always be able to overwrite them for whatever reason. // use \TYPO3\CMS\Core\Cache\Backend\TransientMemoryBackend;$GLOBALS['TYPO3_CONF_VARS']['SYS']['caching']['cacheConfigurations']['myext_mycache'] ??= [];
$GLOBALS['TYPO3_CONF_VARS']['SYS']['caching']['cacheConfigurations']['myext_mycache']['backend'] ??= TransientMemoryBackend::class;  ## Using the Cache¶ First, we need to prepare injection of our cache by setting it up as service in the container service configuration: services: cache.my_cache: class: TYPO3\CMS\Core\Cache\Frontend\FrontendInterface factory: ['@TYPO3\CMS\Core\Cache\CacheManager', 'getCache'] arguments: ['myext_mycache']  The name of the service for the injection configuration is :cache.mycache, the name of the cache is myext_mycache. Both can be anything you like, just make sure they are unique and clearly hint at the purpose of your cache. Note Since TYPO3v10, you should prefer dependency injection to retrieve cache frontends whenever possible and no longer use the CacheManager directly. Here is some example code which retrieves the cache via dependency injection: namespace Acme\MyExt; use TYPO3\CMS\Core\Cache\Frontend\FrontendInterface; class MyClass { /** * @var FrontendInterface */ private$cache;

public function __construct(FrontendInterface $cache) {$this->cache = $cache; } protected function getCachedValue() {$cacheIdentifier = /* ... logic to determine the cache identifier ... */;

// If $entry is false, it hasn't been cached. Calculate the value and store it in the cache: if (($value = $this->cache->get($cacheIdentifier)) === false) {
$value = /* ... Logic to calculate value ... */;$tags = /* ... Tags for the cache entry ... */
$lifetime = /* ... Calculate/Define cache entry lifetime ... */ // Save value in cache$this->cache->set($cacheIdentifier,$value, $tags,$lifetime);
}

return $value; }  Tip It isn’t needed to call has() before accessing cache entries with get() as the latter returns false if no entry exists. Since the auto-wiring feature of the dependency injection container cannot detect which cache configuration should be used for the $cache argument of MyClass, the container service configuration needs to be extended:

services:
Acme\MyExt\MyClass:
arguments:
\$cache: '@cache.my_cache'


Here @cache.my_cache refers to the cache service we defined above. This setup allows you to freely inject the very same cache into any class.