A concept well described in e.g. this thread:
http://www.theserverside.com/news/thread.tss?thread_id=26205
and also in #835

Basically, one could then be able override the getConnection method of such a class:

class foo {
// ...
    public/protected function getConnection()
    {
        return new FooDefaultConnection();
    }
}

with a generated proxy ($this->container auto-injected by some to-be-defined mean):

class extends foo {
    private $container;

    public/protected function getConnection()
    {
        return $this->container('connection_for_foo'):
    }
}

in XML, this could defined with something like e.g.:

<service id="foo" class="foo">
<getter name="getConnection" type="service" id="connection_for_foo" />
</service>

so that $container->get('foo') returns an instance of the generated class (and by this mean an instance of foo of course).

The benefits?

• Lazyness made simple and almost free! I may give it a try;
• immutability (if no corresponding setter exists of course)