Description:
------------
mb_detect_encoding always detect the input string encode as the first in the encoding list supplied, in this case because the first in the list is  UTF-8 always detect as UTF-8, even if the string is  in another encode, if no encoding list is supplied always detect as ASCII.

Reproduce code:
---------------
    function conv2latin($values2conv){
     $encode = mb_detect_encoding($vl2conv, 'utf-8, ISO-8859-1', true);
        if(is_array($values2conv)){
            foreach($values2conv as $key2conv=>$vl2conv){
                $encode = mb_detect_encoding($vl2conv);
                if( strtoupper($encode) != "ISO-8859-1"){
                    $vl2conv = iconv($encode, 'ISO-8859-1', $vl2conv);
                }
              $return[$key2conv]=$vl2conv;
            }
        }elseif(!empty($values2conv)){
           $encode = mb_detect_encoding($vl2conv);
           if( strtoupper($encode) != "ISO-8859-1" ){
                    $return = iconv($encode, 'ISO-8859-1', $values2conv);
                }
        }
        return $return;

return $values2conv;
    }//end function

Expected result:
----------------
The function is pretending to return the string as is if the input string is in ISO-8859-1 if not is pretending to convert the string from UTF-8 to ISO-8859-1 and return the converted string.