in the example below, you would get the same result if you change the function to something like:
function test_ref(&$arr) {
$time = time();
$size = sizeof($arr); // <--- this makes difference...
for($n=0; $n<$size; $n++) {
$x = 1;
}
echo "<br />The function using a reference took ".(time() - $time)." s";
}