In a new post on his blog Matthieu Napoli, creator of PHP-DI, explains how he made v6 much faster.

But the good thing is that, after 6 years of existence, the project has matured and is now quite stable. The original objectives are met, even though there is of course always room for improvements and innovation. There is room to push the container to be better on other levels. And the most obvious one is performances.

PHP-DI 6 will be much, much faster because it is a compiled container.

http://php-di.org/news/21-php-di-6-compiled-container.html