TYPO3 supports the singleton patterns for classes. Singletons are
instantiated only once per request regardless of the number of
GeneralUtility::makeInstance(). To use a singleton
pattern, a class must implement the
class MySingletonClass implements \TYPO3\CMS\Core\SingletonInterface
This interface has no methods to implement.
Be aware that singletons are often considered as "anti pattern" by code architects and should be used with care. Use them only if there are very good reasons.