function euc_substr($str, $start, $charset, $len = NULL) {
		$byte_start = $this->euc_char2byte_pos($str, $start, $charset);
		if ($byte_start === FALSE) {
			return FALSE;
		} // $start outside string length

		$str = substr($str, $byte_start);

		if ($len != NULL) {
			$byte_end = $this->euc_char2byte_pos($str, $len, $charset);
			if ($byte_end === FALSE) // $len outside actual string length
			{
				return $str;
			}
			else
			{
				return substr($str, 0, $byte_end);
			}
		}
		else	{
			return $str;
		}
	}