What?
This is a quick note on one reason you may get the above error in a Joomla CMS environment.


How?
Not really a solution here because this is indicating that the system can't find the core framework files. Yes the bad news is you have lost your site. The good news is that it's only the core files and component files. Here are some tips when restoring the site to return it to as it was.

The error refers to a function used by the core framework. Comment it out and you get an error referring to the includes/framework.php file. Comment that out and you will get errors regarding other elements of the CMS.

This error could have been caused by many things but in the case of one of my clients, the error was due to an update process gone wrong. Not really the fault of Akeeba, Joomla or anyone, it's just one of those things.

Check the sizes of the PHP files on your site and hope that they're not at 0 bytes. Excluding the HOME folder - only check the subfolders. If they are, you've lost the Joomla CMS and you'll need to restore them from a backup.

NOTE: Only restore the files! The images and database were unaffected in our case and could be left as they were. Our last file backup was over a year old but we only needed the core files, a working system, and then we could proceed with a standard Joomla update.

I suspected that part of an auto-update process had corrupted all the files. In our case, the problem was that the system tried to update Akeeba (a 3rd party component to do backups) simultaneously or prior to updating the core Joomla CMS. Ticking both options and then updating re-created the error.

I restored the files (using a backup to overwrite the existing PHP files), leaving the database and images folder unchanged. I updated just the Joomla CMS and then the option to update Akeeba disappeared.

The files backup was over a year old but the content was unaffected, the site was restored to satisfaction... not bad for an hours work.

So I've heard it mentioned before, never thought much of it, but now I know. The lesson here is simply to

Update the Joomla Core separately and prior to any 3rd-party extensions

If you didn't have a backup, then I would simply take a Joomla install (preferably NOT the most recent version - so that you can force it to update later on) and copy over the core files. Get that working and then begin installing any third-party extensions, and then update Joomla Core (by itself) and then any updates to the third-party extensions.