<?php
$a = new stdClass();
for ($i = 0; $i < 10001; $i++) {
    $b =& $a;
    $a->{"a".$i} = $a;
}
unset($b);
$a->b = "xxx";
unset($a);
var_dump(gc_collect_cycles() > 0);
echo "ok\n";
?>