By default Piwik expects UTF-8 encoded strings. Some Tracking API clients or websites are built in non utf8 eg. iso-8859-1
When non utf8 strings are set as "page title" or if Page URL parameters values are encoded in non utf8, we should decode these and reencode in UTF8.
In PHP This ticket will add a new API method to set the charset of strings recorded and tracked in piwik.