Repair accents on php with htmlentities

i want repair the problem of accents , but I have this

error Warning: htmlentities() expects parameter 2 to be long, string given in

my code :

function check_and_secure($T, $field)
{
    if (!isSet($T[$field]))
        return "";
        $in_utf8encoded="é à ù è ò";
       $in_iso8859encoded=iconv("UTF-8", "ISO-8859-1",$in_utf8encoded);
 return   $out_iso8859= htmlentities($T[$field],$in_iso8859encoded, ENT_COMPAT, "ISO-8859-1");

}