public static function from_unicode($a)
	{
		if (! ReflectionTypeHint::isValid()) return false;
		if (is_null($a)) return $a;

		#since PHP-5.3.x iconv() little faster then mb_convert_encoding()
		if (function_exists('iconv'))
		{
			array_walk($a, function(&$cp) { $cp = pack('N', $cp); });
			$s = @iconv('UCS-4BE', 'UTF-8', implode('', $a));
			if (! is_string($s)) return false;
			return $s;
		}
		if (function_exists('mb_convert_encoding'))
		{
			array_walk($a, function(&$cp) { $cp = pack('N', $cp); });
			$s = mb_convert_encoding(implode('', $a), 'UTF-8', 'UCS-4BE');
			if (! is_string($s)) return false;
			return $s;
		}

		return implode('', array_map(array(__CLASS__, 'chr'), $a));
	}