ZF-5637: Wrong handling of UTF8 strings length.
Before sending a tweet or direct message, the library checks for the length of the message for length. It uses strlen to do that, which returns wrong length for UTF8 strings. The correct way to do this is using the mb_strlen function.
I couldn't find how I can comment on the issue too, so here's my reply to Thomas: If you mean to use iconv to convert to something not multibyte, do strlen and then run iconv again - that might work. Otherwise it won't, because Twitter expect the input in UTF8.