@jmikola, I've just pushed the updated commits. For now, I've decided against amending the existing commits in order to better highlight the development. I'll squash the changes if you feel this is ready to get merged.

this will be merged to a 0.3 branch […]

I understand your reluctance in adding BC hacks and understand you consider the $that = $this assignment being one such hack. I've deliberately tried to keep the changes in this PR to a minimum to highlight that tossing compatibility with PHP 5.3 is an arbitrary (politic) decision not imposed by technical limitations. Assuming we were to find a way that avoids hackery but involves a slightly bigger changeset, would this still land in a dedicated and deprecated branch that gets overwritten immediately after?

My motivation for filing this PR is BC with PHP 5.3 so that (any version of) this project can be used with PHP 5.3. As such, dropping support in future versions again isn't really a major concern admittedly. I'm just trying to understand the rationale in intentionally limiting BC in the future.