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 and usage

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.

if (!is_array($GLOBALS['TYPO3_CONF_VARS']['SYS']['caching']['cacheConfigurations']['myext_mycache'])) {
    $GLOBALS['TYPO3_CONF_VARS']['SYS']['caching']['cacheConfigurations']['myext_mycache'] = array();
}

Tip

The is_array() check is done 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 selection is again encapsulated in a if (!isset()) check 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.

if (!is_array($GLOBALS['TYPO3_CONF_VARS']['SYS']['caching']['cacheConfigurations']['myext_mycache'])) {
    $GLOBALS['TYPO3_CONF_VARS']['SYS']['caching']['cacheConfigurations']['myext_mycache'] = array();
}
if (!isset($GLOBALS['TYPO3_CONF_VARS']['SYS']['caching']['cacheConfigurations']['myext_mycache']['backend'])) {
    $GLOBALS['TYPO3_CONF_VARS']['SYS']['caching']['cacheConfigurations']['myext_mycache']['backend'] = 'TYPO3\\CMS\\Core\\Cache\\Backend\\TransientMemoryBackend';
}

To get an instance of a cache, GeneralUtility::makeInstance('TYPO3\\CMS\\Core\\Cache\\CacheManager')->getCache('myext_mycache') should be used. The cache manager will return the fully initialized cache instance:

$myCacheInstance = GeneralUtility::makeInstance('TYPO3\\CMS\\Core\\Cache\\CacheManager')->getCache('myext_mycache');

Cache access logic

Cache usage patterns are usually wrappers around the main code sections. Here is some example code:

protected function getCachedMagic() {
    $cacheIdentifier = $this->calculateCacheIdentifier();
    $cache = GeneralUtility::makeInstance('TYPO3\\CMS\\Core\\Cache\\CacheManager')->getCache('myext_mycache');

    // If $entry is null, it hasn't been cached. Calculate the value and store it in the cache:
    if (($entry = $cache->get($cacheIdentifier)) === FALSE) {
        $entry = $this->calculateMagic();

        // [calculate lifetime and assigned tags]

        // Save value in cache
        $cache->set($cacheIdentifier, $entry, $tags, $lifetime);
    }
    return $entry;
}

Tip

It isn't needed to call has() before accessing cache entries with get() as the latter returns FALSE if no entry exists.