If the DB saves data in UTF8, then "exporting to excel" will output wrong encoded characters(for multi-bytes characters such as Chinese or Japanese).

I find that, this problem is caused by this function "excel_prepare_string()" in "excel_api.php:

$t_ret .= utf8_encode($t_value);

This is not correct if the DB saves data in UTF8. In such case, it should be:

$t_ret .= $t_value;

I think you should judge the DB encoding before doing the utf8_encode.