Running multiple generator simultaneously

generator.php

<?php

$epoch = microtime(true);

function times(int $a) {
	global $epoch;
	$i = 0;
	while (++$i <= $a) {
		//sleep(1);
		var_dump(microtime(true) - $epoch);
		yield $i.'/'.$a;
	}
}

$aAndB = new AppendIterator();
$aAndB->append(times(10));
$aAndB->append(times(5));

$both = new MultipleIterator(MultipleIterator::MIT_NEED_ANY);
$both->attachIterator(times(10));
$both->attachIterator(times(5));

foreach ($both as list($i,$j)) {
	sleep(1);
	var_dump($i,$j);
}
/*
float(1.8119812011719E-5)
float(4.7922134399414E-5)
float(5.1975250244141E-5)
string(4) "1/10"
string(3) "1/5"
float(1.0001580715179)
float(1.000167131424)
string(4) "2/10"
string(3) "2/5"
float(2.0002980232239)
float(2.0003049373627)
string(4) "3/10"
string(3) "3/5"
float(3.0004329681396)
float(3.0004439353943)
string(4) "4/10"
string(3) "4/5"
float(4.0005650520325)
float(4.0005760192871)
string(4) "5/10"
string(3) "5/5"
float(5.0006899833679)
string(4) "6/10"
NULL
float(6.0007889270782)
string(4) "7/10"
NULL
float(7.0009140968323)
string(4) "8/10"
NULL
float(8.0010290145874)
string(4) "9/10"
NULL
float(9.0011451244354)
string(5) "10/10"
NULL
*/