Encoding::convert

static function convert($data, $charsetFrom, $charsetTo)
{
	if (is_array($data) || $data instanceof SplFixedArray)
	{
		//let's do a recursion
		if ($data instanceof SplFixedArray)
		{
			$result = clone $data;
		}
		else
		{
			$result = [];
		}
		foreach ($data as $key => $value)
		{
			$newKey = self::convert($key, $charsetFrom, $charsetTo);
			$newValue = self::convert($value, $charsetFrom, $charsetTo);

			$result[$newKey] = $newValue;
		}
		return $result;
	}
	elseif (is_string($data))
	{
		if ($data == '')
		{
			return '';
		}
		return static::convertByMbstring($data, $charsetFrom, $charsetTo);
	}
	return $data;
}