php ctype_alpha与setlocale

I'm using ctype_alpha to check if name is entered correctly. This is the code:

Get $ime:

$ime = mysql_real_escape_string($_POST["ime"]);

Check $ime:

if (!ctype_alpha(str_replace(array(
    "'",
    "-",
), "", $ime))) {
    header("Location: error.php?error=14");
    break;
}

I'm from Croatia, and we have characters like: "č", "ć", "š", ... So i tried to add setlocale function:

setlocale(LC_ALL, 'hr_HR','hrv_HRV', 'hr', 'hrv', 'croatian', 'hrvatski', 'Croatian', 'Hrvatski', 'hr_HR.utf8');

But still after using characters "č", "ć", "š" it throws me an error (redirect to error.php?error=14)

Is there any other way to solve this, because I really need to be able to use those characters?