public static function is($string, array $options = []) {
		$defaults = ['quick' => false];
		$options += $defaults;

		if ($options['quick']) {
			$regex = '/[^\x09\x0A\x0D\x20-\x7E]/m';
		} else {
			$regex  = '/\A(';
			$regex .= '[\x09\x0A\x0D\x20-\x7E]';
			$regex .= '|[\xC2-\xDF][\x80-\xBF]';
			$regex .= '|\xE0[\xA0-\xBF][\x80-\xBF]';
			$regex .= '|[\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}';
			$regex .= '|\xED[\x80-\x9F][\x80-\xBF]';
			$regex .= '|\xF0[\x90-\xBF][\x80-\xBF]{2}';
			$regex .= '|[\xF1-\xF3][\x80-\xBF]{3}';
			$regex .= '|\xF4[\x80-\x8F][\x80-\xBF]{2}';
			$regex .= ')*\z/m';
		}
		return (boolean) preg_match($regex, $string);
	}