Basically it says that instead of calling the framework and invoking it’s objects, you would make the framework aware of your objects. How Michael Mattson’s would say, this is the Hollywood Principle: “Do not call us, we call you”.
There are some good proposals of developing the Injection Container for the Zend Framework, but so far, at this moment looks like there isn’t any really developed therefore you can find a good library to take a look at Symfony Components.
Check out this article from Ibuildings. I has a good perspective of how it could be developed with the Zend Framework.