function isUtf8($string)
{
    if (is_object($string))
    {
        throw new Exception('Input cannot be an object!');
    }

    elseif (is_array($string))
    {
        foreach($string as $key => $value)
        {
            if (!strings_is_utf8($value))
                return false;
        }

        return true;
    }

    return preg_match('%(?:
                         [\xC2-\xDF][\x80-\xBF]                 # non-overlong 2-byte
                         |\xE0[\xA0-\xBF][\x80-\xBF]            # excluding overlongs
                         |[\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}     # straight 3-byte
                         |\xED[\x80-\x9F][\x80-\xBF]            # excluding surrogates
                         |\xF0[\x90-\xBF][\x80-\xBF]{2}         # planes 1-3
                         |[\xF1-\xF3][\x80-\xBF]{3}             # planes 4-15
                         |\xF4[\x80-\x8F][\x80-\xBF]{2}         # plane 16
                         )+%xs', $string);
}