Multibyte characters in URL are not rendering

I have a bugging problem. For a website I made there are search engine friendly URL's generated. The only problem is there are ß-chars in the url too. Chars like ö, ï, ä, ü etc. are placed correct. But with the ß-char there is a diamond-icon with a questionmark in it. -> �

I thought it had to do with the charset which is used but i've tried both UTF-8 and iso-8859-1. Both without luck.

I need to have the co开发者_JAVA百科rrect character in the url for the readability of deeplinks.

does the character U+00DF in UTF8 work with you? i tried to use it on Firefox and the URL was translated into ss

in URL encoding, the U+00DF should be translated to %DF

Thanks for your answers, both + 1. I've solved the problem by using the iconv function, which is installed by default.