smoked

function mb_str_split($string) {
    $length = mb_strlen($string, "utf-8");

    $i = 0;
    $arr = array();
    while ($i < $length) {
        $rep = mb_substr($string,$i,1,"utf-8");
        array_splice($arr, $i, 1, $rep);
        $i++;
    }

    return $arr;
}


function transcode($string) {
    $string = mb_str_split($string);
     
    $string = array_map(function($a) {
        $result = unpack('N', mb_convert_encoding($a, 'UCS-4BE', 'UTF-8'));

        if (is_array($result) === true) {
            return $result[1];
        }
    }, $string);

    return implode("", $string);  
}
        
$string = "аАБВГДЕЁЖЗ";
echo transcode($string);

$val = array_map(function($a){ return "{".$a."}"; }, array_values($arr));