I just upgraded to 3.1, and after refreshing I get the following error:

Fatal error: Call to undefined function wp_cache_get() in /public_html/blog/wp-includes/functions.php on line 336

A quick google search led me to this post on WordPress support forum, however I tried disabling all plugins as suggested, and I'm using TwentyTen as my only theme.

I also set define('WP_CACHE', false) in the config, didn't help...

Any ideas before I attempt to roll everything back?

Any ideas?

  • I'd guess a plugin at fault, disable all your plugins and see if you're able to run the upgrade as Marja pointed out, wp-admin/upgrade.php (they don't need to be disabled permanently, just long enough to get your site working again).
    – t31os
    Commented Feb 24, 2011 at 17:59
  • @t31os: I tried, unfortunately I got the error on every page. I ended up reverting to 3.0.5 (from backup)... Commented Feb 24, 2011 at 19:37

3 Answers 3


Do you have a object-cache.php in your wp-content directory? If so, rename it.
But first make sure the upgrade replaced all new files. Upgrade per FTP and watch out for failed transfers.


I had problems upgrading too. Not the same as you though. I got a complete blank screen after entering my login details.My sites worked fine at the frontend though. The plugin option didn´t work for me either. What I did was ran(It´s a local setup): http://localhost/wordpress/wp-admin/upgrade.php

I could then get in to my admin again, Finnish the database update and run the 3.1 upgrade Basically I just followed the messages at the top of my screen again and now I´m all fine!

Hope it helps!

  • I wish... I can't even get to the admin page! Commented Feb 24, 2011 at 13:08

The problem was linked to the WP-Hive plugin, and it was (partially) resolved, when the plugin's author had fixed the problem.

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