Exchanging currencies with Zend_Currency_CurrencyInterface

As many companies offering online services do, we handle multiple currencies. This often involves querying external services to know the real value of the currency exchange. Previously, this logic was scattered all over the code, even copy-pasted in multiple files, and is pretty hard to mantain, let alone to test.

So, in my work detecting and extracting patterns from old spaghetti code, I came with the following solution: A Service layer.

How to detect if a class implements an Interface?

I'm in the real need to know if, given a string className or object, it implements a particular interface. I'm specially interested in the string className part.

During the search, many seemingly valid options appeared: instanceof, is_subclass_of, is_a, ReflectionClass::ImplementsInterface, class_implements… Which one to use? Let's do some testing!