word_wrap in Email.php (library) does not handle multibyte characters well.
It made long line of plaintext Chinese characters look weird when it cuts multibyte characters in the middle.
Could you try something out?
Go here http://php.net/manual/en/function.wordwrap.php and check out the contributed function iconv_wordwrap by "mail at dasprids dot de".
Put the same Chinese characters through that string, then let us know how it goes.
Sure. I will give it a try this weekend. Hope it is not too late.
Some improvements have been made, but it's still not flawless ... I'm not sure it can ever be. If anybody has feedback - please comment.
So let me preface this by saying that my C knowledge is (almost) nonexistent.
PHP's wordwrap function uses strncmp, which operates on char's, which are 1 byte, as opposed to wstrcmp which can handle multi-byte characters... so the C code behind the wordwrap function sees your multi-byte character as 2 separate characters.
This can be fixed in 1 of 2 ways:
1) Re-writing the word_wrap function to not use php's wordwrap() and instead write our own version. This will be slower, but should work if we use mb_strlen() for calculations instead of strlen().
2) Add a mb_wordwrap() function to PHP, and then use that instead.
I don't have time to see which function works properly, but the wordwrap() function in the Email class could possibly be replaced by something here: http://stackoverflow.com/questions/3825226/multi-byte-safe-wordwrap-function-for-utf-8
Adding a multibyte wordwrap function to PHP is probably a bit beyond the scope of this project.
However, there are several examples of multibyte wordwrap functions at http://stackoverflow.com/questions/3825226/multi-byte-safe-wordwrap-function-for-utf-8
Any of those could be adapted/extended/coopted.