A really detailed generators tutorial - this one looks really informative and relevant because it goes over the use of yield in conjunction with array_map and array_reduce and various other collection-related classes
Memory performance boosts with generators and nikic/iter - EXTREMELY useful, extremely relevant generators article about working with generators and CSV data and collection-like functionality. It basically has everything I'm working on right now.
Write a generator function that can wrap any iterator or iterable. It would be used like this (I think... I'm still pretty new to generators).
Research / Resources