natsort and strnatcasecmp work different with cyrillic

strnatcasecmp works very strange with cyrillic. See code:

//must be exact in this order
$s1 = 'Журнал 1';
$s2 = 'Каротаж';

$arr[] = $s1;
$arr[] = $s2;
natsort($arr);
//worked fine
var_dump($arr);

var_dump(strnatcasecmp($s1, $s2));
//returns 1 although must return -1!

Answer

Eventually, I resolved the problem like this:

function strnatcasecmp_cyr($s1, $s2)
{
    if ($s1 === $s2) {
        return 0;
    }
    $arr[] = $s1;
    $arr[] = $s2;
    natsort($arr);
    if (current($arr) === $s1) {
        return -1;
    } else {
        return 1;
    }
}

Pretty ugly, but it did the trick. Look forward for better solution.