after autoupdating I have login page with the following text:
To run Piwik you need at least PHP version 5.3.3
Unfortunately it seems your webserver is using PHP version 5.3.2-1ubuntu4.27.
Please try to update your PHP version, Piwik is really worth it! Nowadays most web hosts support PHP 5.3.3.
Also see the FAQ: My Web host supports PHP4 by default. How can I enable PHP5?
I can’t login anymore. For several reasons I can not update PHP to 5.3.3. How can I go back to 2.5 ?
BTW: would it not be better to check this before the update