The presentation starts with some basic theory on types. Later, different classifications for type systems are described, with the static/dynamic and strong/weak dimensions the ones we spend more time on.
The third topic addressed is how the mix of polimorsfism with covariance and descendant hiding affects the type system, and what new problems arise and have to be addressed by the type system.
We finished the presentation with a discussion about pros and cons of the PHP type system.
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