Differing results between php and hhvm.

generator-discrepancy.php

<?php

use Rx\Observable;
use Rx\Operator;

require_once "vendor/autoload.php";

function rangeGenerator($start, $end)
{
    for ($i = $start; $i <= $end; $i++) {
        yield $i;
    }
}

$source = Observable::fromIterator(rangeGenerator(0, 12));

$stream = $source
    ->subscribe(new \Rx\Observer\CallbackObserver(
        function ($x) {
            echo var_dump($x);
        }
    ))
;

foreach (rangeGenerator(0, 12) as $x) {
    var_dump($x);
}