문자열 절반 마킹

/**
 * 문자열 절반 마킹
 * @param string $str
 * @param int $char
 * @param string $charset
 * @return string
 */
function marking($str, $char = '*', $charset = 'UTF-8') {
    $len = mb_strlen($str, $charset);
    $pos = ceil($len / 2);
    if($len > 14)
        return str_repeat($char, $len - $pos).mb_substr($str, $pos, $len - $pos, $charset);
    else
        return mb_substr($str, 0, $pos, $charset).str_repeat($char, $len - $pos);
}