+/* This implementation supports two modes:
+ * - entering the OP Identifier, which can simply be 'polytechnique.org'
+ * - entering the User Identifier, or some URL that resolves there
+ * In both cases, Yadis discovery is made possible through the X-XRDS-Location
+ * header.
+ *
+ * In the former case, Yadis discovery is performed on /, or where it redirects;
+ * see platal.php. It resolves to the XRDS for this OP, and User Identifier
+ * selection is performed after forcing the user to log in. This only works for
+ * version 2.0 of the OpenId protocol.
+ *
+ * In the latter cas, Yadis discovery is performed on /openid/{hruid}. It
+ * resolves ta a user-specific XRDS. This page also features HTML-based
+ * discovery. This works with any version of the protocol.
+ */
+
+/* Testing suite is here:
+ * http://openidenabled.com/resources/openid-test/
+ * It only supports User Indentifiers.
+ *
+ * To test OP Identifiers, download the JanRain PHP library and use the
+ * consumer provided as an example (although it appears that a failure is
+ * mistakenly reported: 'Server denied check_authentication').
+ * Reading the source of the server can also help understanding the code below.
+ */
+
+