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Ruby 1.9.x and later (at least in MRI) also guarantee to iterate over hash elements in the order in which keys were inserted.

http://www.ruby-doc.org/core-1.9.3/Hash.html

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Yes, and I think I can safely say I've never used this feature (in either Ruby or PHP) for anything more serious than a code golf challenge.

This might just be me, but I don't think an ordered hash is a particularly easy data structure to reason about. Almost all the code that I've seen depend on it in either language has been too clever by half.

I've used it when I want to parse query params from a URL into a hash, and then possibly modify them, and then write them back out to query params -- in the same order they came in, so the query params will be identical if I didn't end up modifying them, and identical but for what I modified otherwise, etc.

There are probably other analagous circumstances. Maybe even some I could think of that I've encountered.

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