Problem with ctype_alnum and spanish characters

I have this on my source code, but it does not work:

PHP:

setlocale(LC_ALL, 'es_CL.utf8');

// Do add result
$clean = array();
if (isset($_POST["name"]) && !empty($_POST["name"]) && ctype_alnum($_POST["name"]) && strlen($_POST["name"]) < 50) {
        $mysql["name"] = clean_input($_POST["name"]);
}


And the locale is there:

Code:

dan@www:~$ locale -a | grep CL
es_CL.utf8

I want ctype_alnum to recognize characters like á,ó,ú, etc... is this possible? someone has done it?
Thanks.

 

This is an alternative solution:

PHP:

// _ctype_alnum accepting spanish chars
function _ctype_alnum($string)
{
    $convert = array(
                    "á"=>"a", "é"=>"e", "í"=>"i", "ó"=>"o", "ú"=>"u", "ñ"=>"n",
                    "Á"=>"A", "É"=>"E", "Í"=>"I", "Ó"=>"O", "Ú"=>"U", "Ñ"=>"N"
                    );
    $string = strtr($string, $convert);
    return ctype_alnum($string);
}