One important thing to remember is that in iterator can be infinite. Not all iterators necessarily end. If iterator_to_array is used on such an iterator, it will exhaust the available memory, and throw a fatal error.
For example, consider the following code:
<?php
function fibonacci(): Generator
{
yield $a = 1;
yield $b = 2;
start:
yield $c = $a + $b;
$a = $b;
$b = $c;
goto start;
}
$fibonacciSequence = fibonacci();
iterator_to_array($fibonacciSequence);
?>
Since <?php fibonacci(); ?> generates an infinite fibonacci sequence, which is valid, since it is actually an infinite sequence, then attempting to convert it to an array will fail.
