There are several problems with handling multi byte strings in the frontend.
1. The frontend cannot properly work with mbstring.func_overload enabled. We must require it to be disabled.
2. We need to review the usages of the PHP string functions and our zbx wrappers and replace them with mbstring functions. Since we require mb string to be enabled, our zbx wrappers must be removed.
3. For mb string functions to work properly we must set the internal encoding to UTF-8.