After upgrading a ExpressionEngine 2.1.0 site to ExpressionEngine 2.5.2 (ran into issues trying to upgrade to 2.7.3 and 2.5.2 was the oldest I had in my archives) I am running into a white screen when trying to access Edit Sites or any of the two sites under the Site Name menu in the ExpressionEngine CP.

I've enabled debugging output everywhere I can think of — in the CP, in index.php files, etc. — but still only see the white screen.

I am trying to do this with MSM 2.1.6.

Any thoughts on what to check for this? Configuration settings that might have been missed? Something in the database that might not have been updated properly between 2.1.0 and 2.5.2? That sort of thing.

UPDATE (2014/03/10)

I was able to uncover a couple more useful data points. When I try to load the Edit Sites screen in Chrome, I see this error message:

Fatal error: Class 'CP_Controller' not found in /Users/bseymore/Sites/backspaceink-252.loc/admin/expressionengine/controllers/cp/sites.php on line 25

For some reason that error message does not appear in Safari.

When I try to load the Edit Sites screen via Safari, I see this in the Developer Console:

Failed to load resource: the server responded with a status of 500 (Internal Server Error) http://[SITE-NAME]/admin/index.php?S=e34bf993965b3c69ce41729920acdf886e3e4dba&D=cp&C=sites&M=manage_sites

  • What are in the response headers? Also, I work at The Weekly now and thought I'd say hello; I recognize your name because Cedric brings it up from time to time. Mar 10, 2014 at 1:36
  • Glad to meet you! Hopefully he has good things to say about me. :-) As you'll see I was finally able to get an error message to appear and resolve the issue. MSM is a feisty little devil. Mar 11, 2014 at 0:04

1 Answer 1


After a little bit of poking around, I found a thread in the archived EllisLabs forums with the solution. I needed to make a couple small edits to /controllers/cp/sites.php to get up and running.

My hunch is MSM 2.1.6 was not quite compatible with 2.5.2 and so rolling back to an the slightly edited older version of MSM got me moving again.

For future reference, the thread is right here:


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