PHP generator return type

Question

I've never used generators in PHP before and there are no examples in the documentation that show the return type declaration.

In PhpStorm, there is an error in the IDE when I do this:

public function getDataIncrementally(): void {
    yield from [/* some large set of numbers*/];
}

The error is:

Generators may only declare a return type of Generator, Iterator or Traversable, or iterable, void is not permitted.

I can see the inheritance tree is Traversable -> Iterator -> Generator. Meanwhile, iterable is a new pseudo-type introduced in PHP 7.1.

Would it be appropriate to use iterable for the return type declaration if I only need to support PHP >= 7.1?

Answer 1

Your return type is Generator, but you are using void. Try the following:

public function getDataIncrementally(): \Generator {
    yield from [/* some large set of numbers*/];
}