src/StringHelper.php
public static function rtrim($str, $charlist = false)
	{
		if (empty($charlist) && $charlist !== false)
		{
			return $str;
		}

		if ($charlist === false)
		{
			return utf8_rtrim($str);
		}

		return utf8_rtrim($str, $charlist);
	}
public static function rtrim($str, $charlist = false)
	{
		if (empty($charlist) && $charlist !== false)
		{
			return $str;
		}

		if ($charlist === false)
		{
			return utf8_rtrim($str);
		}

		return utf8_rtrim($str, $charlist);
	}
UTF-8 aware replacement for rtrim()

Strip whitespace (or other characters) from the end of a string. You only need to use this if you are supplying the charlist
optional arg and it contains UTF-8 characters. Otherwise rtrim will work normally on a UTF-8 string.

@param   string  $str       The string to be trimmed
@param   string  $charlist  The optional charlist of additional characters to trim

@return  string  The trimmed string

@link    https://www.php.net/rtrim
@since   1.3.0