TYPO3 Core

After the ISP updated to PHP 5.2.6, the Typo3 backend was no longer vailable. Instead of the login screen, a PHP error came up reporting a safe-mode conflict. It turned out that PHP's parameter session.save_path was not initialised, and the default directory (/var/tmp) was not accessible in safe mode.
I needed to set "session.save_path to a new and accessible directory, in php.ini. When I did, everything worked again.

Unfortunately, not every ISP allows the user to make his own php.ini; and these ISPs more often than not have their servers in safe mode permanently and by default.
So it may be necessary to change typo3/install/index.php to include a call to session_save_path() with an appropriate value prior to calling start_session(). The value (path) to be used should be defined in the configuration.

(issue imported from #M9155)