The latest version of WordPress is v4.7. It is always recommended to upgrade to the latest released to minimize vulnerabilities (exposure) and improve use of content management service.
Always backup before you upgrade, copy your WordPress files and download the database. This will give us way to roll-back just in case we run into “unknown” issue. It is not always perfect when you upgrade.
During my upgrade to v4.7 to one of my customer website. I’ve got this error.
Fatal error: Call to a member function do_all_hook() on a non-object in /home/public_html/wp-includes/plugin.php on line 837
A quick fix is to re-upload the plugin.php file from my old backup to the /wp-includes folder. This works!
But I want to use the latest plugin.php file not the old copy. Searching the internet trying to find out if anyone has encounter the same error when upgrading to the latest version of wordpress. No surprise! It is already been discussed, issue and alternative solutions to fix it.
I found the solution. I disabled this file “/wp-content/object-cache.php” by renaming it to object-cache.DISABLED.php or deleting will work as well. I don’t know the use of this file at this point.
I re-uploaded the latest plugin.php to /wp-includes/ folder. Tested my website and happy with the result.
I hope this help.