What are cache groups

In the TYPO3 caching framework, there are currently three types of caches:

• pages : Front-end related caches
• system : Low-level caches that shouldn’t normally be flushed
• all : All other caches that don’t fall into one of the two categories before

Based on the cache type (a.k.a cache group) the caches are flushed on different occasions. This makes a difference for the editors because depending on what they have changed, most often one of the cache groups will be flushed as well. Also, there are at least two options available when editors decide to flush the caches manually:

The first option will only flush front-end related caches while the second one flushes all caches that are not in the “system” or “pages” cache group. Flushing the “system” caches isn’t that easy any more but those don’t need to be cleared at all by editors. Instead, they are automatically flushed if e.g. a new extension is installed.

Therefore, it makes sense to tell TYPO3 which cache group your cache should be in if you use the caching framework to store data temporarily. This allows at least editors to selectively flush caches instead of the famous “flush all caches to be sure”! More information about which cache in in which cache group can be found in the article about the TYPO3 caching architecture.

Set up your extension cache

To create your own cache in your TYPO3 extension, there are only a few lines in the ext_localconf.php of your extension necessary. You can copy and paste these lines and only have to replace the aimeos string by the name of your own TYPO3 extension:

if( !is_array( $TYPO3_CONF_VARS['SYS']['caching']['cacheConfigurations']['aimeos'] ) ) {
    $TYPO3_CONF_VARS['SYS']['caching']['cacheConfigurations']['aimeos'] = array();
}
 
if( !isset($TYPO3_CONF_VARS['SYS']['caching']['cacheConfigurations']['aimeos']['frontend'] ) ) {
    $TYPO3_CONF_VARS['SYS']['caching']['cacheConfigurations']['aimeos']['frontend'] = 'TYPO3\\CMS\\Core\\Cache\\Frontend\\StringFrontend';
}
 
if( !isset($TYPO3_CONF_VARS['SYS']['caching']['cacheConfigurations']['aimeos']['backend'] ) ) {
    $TYPO3_CONF_VARS['SYS']['caching']['cacheConfigurations']['aimeos']['backend'] = 'TYPO3\\CMS\\Core\\Cache\\Backend\\DatabaseBackend';
}
 
if( !isset($TYPO3_CONF_VARS['SYS']['caching']['cacheConfigurations']['aimeos']['options'] ) ) {
	$TYPO3_CONF_VARS['SYS']['caching']['cacheConfigurations']['aimeos']['options'] = array( 'defaultLifetime' => 0 );
}
 
if( !isset($TYPO3_CONF_VARS['SYS']['caching']['cacheConfigurations']['aimeos']['groups'] ) ) {
	$TYPO3_CONF_VARS['SYS']['caching']['cacheConfigurations']['aimeos']['groups'] = array( 'pages' );
}

The whole if/is_array/isset thing is necessary to allow administrators to overwrite your settings in the typo3conf/LocalConfiguration.php file as the configuration of your extension is loaded afterwards. Thus, it would overwrite any previous configuration settings if you don’t check first if they exist.

There are four settings you can use to configure your cache in the TYPO3 caching framework:

• frontend : What type of data is accepted
• backend : Where is the data stored
• options : Additional configuration settings for the back-end
• groups : The cache groups your extension cache belongs to

There’s the choice between two cache front-ends and several cache back-ends. A complete list of both including their options is available in the TYPO3 cache front-end/back-end article. The groups setting can be either pages, system, all or a combination thereof. Normally, you should use only one cache group and the group all is the default value if you don’t specify one.

Use your new cache

Once set up, you can access the cache everywhere in you TYPO3 extension and you only have to write a few lines:

$name = 'TYPO3\\CMS\\Core\\Cache\\CacheManager';
$manager = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance( $name );
$cache = $manager->getCache( 'aimeos' );

They create an instance of the cache manager and retrieve your cache by name. Replace aimeos with the name of your extension resp. the name you’ve used in your ext_localconf.php in the cache setup code. Now you are able to set and get cached entries or remove them from the cache again:

$cache->set( 'auniqueidentifier', $data, array( 'tag1', 'tag2' ) );
$data = $cache->get( 'auniqueidentifier' );
$cache->remove( 'auniqueidentifier' );

So, let’s go and make your TYPO3 extension fast!