"Cannot redeclare class themeregistry" when trying install Drupal 7
When attempting to install Drupal 7 on a server which has a few Drupal 6 installs running without a problem I got a white screen of death after selecting the profile I want to use.
Looking in the log file were quite a few lines stating:
[Wed Feb 08 10:19:55 2012] [error] [client 18.104.22.168] PHP Fatal error: require() [function.require'>function.require]: Cannot redeclare class themeregistry in /var/www/microsites/www/includes/install.inc on line 1120
The problem turned out to be an issue with an APC configuration.
In your apc.ini file change the following:
The apc.ini file on this RedHat server was located in /etc/php.d/apc.ini.