단어 경계를 유지하면서 멀티바이트 문자열을 정확하게 자를 수 있는 방법은 무엇입니까?

function truncate($string, $chars = 50, $terminator = ' …') {
    // Calculate the maximum length considering the terminator
    $max_length = $chars - mb_strlen($terminator);

    // Short circuit for strings shorter than the maximum length
    if (mb_strlen($string) <= $max_length) {
        return $string;
    }

    // Find the last space character within the maximum length
    $last_space_index = mb_strrpos($string, ' ', $max_length);

    // Cut the string at the last space or at the maximum length if no last space is found
    $truncated_string = (false !== $last_space_index)
        ? mb_substr($string, 0, $last_space_index)
        : mb_strimwidth($string, 0, $chars);

    // Append the terminator
    $truncated_string .= $terminator;

    return $truncated_string;
}

$in = "Answer to the Ultimate Question of Life, the Universe, and Everything.";
$out = truncate($in, 50, ' …');

echo $out; // "Answer to the Ultimate Question of Life, the …"