Tuples need because they more simple for understand and matching then lists and strings. Tuples can simple converts to lists and back. Tuples more effective with memory.
Only one class can implement tuples now its SplFixedArray. But there bugg when you call createFromArray in own custom class derived from SplFixedArray. Also with small count uts slow.
Try test Erlang and see his power. I hope you think will too, that PHP needs with Erlang features.
