Singletons

TYPO3 supports singleton patterns for classes. Singletons are instantiated only once per HTTP request regardless of the number of calls to GeneralUtility::makeInstance(). To use a singleton pattern, a class must implement the SingletonInterface:

namespace Vendor\MyNamespace;

class MySingletonClass implements \TYPO3\CMS\Core\SingletonInterface
{
    …
}

This interface has no methods to implement.