Problems with Zend_Service_Amazon_Simpledb and specialchars

I want to copy some data from MySQL to SimpleDB with the Zend Framework. It works fine so far, but if any attribute contains special chars like "äöüß" the server refused my request with "The request signature we calculated does not match the signature you prov开发者_如何学编程ided.".

SimpleDB accept the request, if all specialchars are encoded in some way, but I want it like it is. What can I do to solve that? I tried to find informatione in google, but I found no solution.

I found a solution for that problem, but I had to change some code in Zend_Service_Amazon_SimpleDb. There was a missing http-header in the request. Just add

$request->setHeaders('Content-Type', 'application/x-www-form-urlencoded; charset=utf-8');

in _sendRequest().