- https://phptherightway.com/pages/Design-Patterns.html#singleton - https://blog.cotten.io/how-to-screw-up-singletons-in-php-3e8c83b63189 - https://stackoverflow.com/a/203359/1348344 - https://github.com/TomasVotruba/zend-framework-1-tutorial/search?p=1&q=singleton&unscoped_q=singleton
https://phptherightway.com/pages/Design-Patterns.html#singleton
https://blog.cotten.io/how-to-screw-up-singletons-in-php-3e8c83b63189
https://stackoverflow.com/a/203359/1348344
https://github.com/TomasVotruba/zend-framework-1-tutorial/search?p=1&q=singleton&unscoped_q=singleton