Though the generators look cool, I've never used them much because I didn't find a good use case. Evert Pot  demonstrates on his blog how they can help conserve memory.

Since the release of PHP 5.5, we now have access to generators. Generators are a pretty cool language feature, and can allow you to save quite a bit of memory if they are used in the right places.

http://evertpot.com/switching-to-generators/