+ Persistent handles and "cookiestore" request option do interfere,
+ as libcurl saves the cookies to the file on curl_easy_destroy(),
+ cookies are not saved until the CURL handle will be recycled.
+ Thus one would either need to
+ * run PHP with http.persistent.handles.limit = 0
+ * call http_persistent_handles_clean() every request
+ * call $HttpRequest->flushCookies(), which is available
+ since libcurl v7.17.1 and does not work with the
+ procedural API
+ Anyway, none of these options is really perfect.
+ HTTP and Proxy authentication information (username/password) can not be
+ unset with NULL prior libcurl v7.19.6 and separate options for setting
+ username and password--which work--are only available since v7.19.6.