Errors how to fix?

Question

Joomla

After upgrading from version 2.5 to 3.8 site shows white screen and errors
Warning: Cannot redeclare class jregistry in /home/users/arxizm_jm3/site/libraries/loader.php on line 673
Fatal error: Call to undefined method JApplicationHelper::getHash() in /home/users/arxizm_jm3/site/libraries/src/Application/CMSApplication.php on line 738
what is the reason for this please tell me? Is it a template issue or a plugin issue?

Answer 1

Not in a template and not in plugins. The Joomla update was probably done incorrectly. DO NOT upgrade from 2.5 directly to 3.8, this will lead to the inoperability of the site. Here is the official step-by-step instruction for this kind of update, and it says in English and white: Warning! Joomla! 2.5.28 can only be migrated in two steps. First migrate to version 3.5.1 . Then upgrade from version 3.5.1 to the latest 3.x version using the one-click installer. In Russian, this means that you should first update (by any available method) Joomla to 3.5.1, and then upgrade to 3.8 through "Components - Joomla Update".
Describe how Joomla was updated. I can assume that you just rolled it from the archive over the old site? Did you make a preliminary backup of the site? If not, then it's just a pipe.