Extend all container instance checks with psr interface Psr\Container\ContainerInterface. methods signature are equal not change needed.

Documentation:

• https://github.com/php-fig/fig-standards/blob/master/proposed/container.md
• [DI] Implement PSR-11 symfony/symfony#21265
• http://symfony.com/blog/new-in-symfony-3-3-psr-11-containers