Fix WordPress W3 Total Cache “Uncaught Exception Unknown Engine” 500 Fatal Error

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W3 Total Cache uncaught Exception Unknown Engine 500 Fatal Error
W3 Total Cache uncaught Exception Unknown Engine 500 Fatal Error
So recently I changed hosting providers for one of my WordPress webpage and all of a sudden I kept getting 500 Fatal Errors when I tried to publish a new post. It would maybe seem that it was the hosts fault but after inspecting some logs I came across this:

Fatal error: Uncaught Exception: unknown engine in /PATH/TO/FOLDER/wp-content/plugins/w3-total-cache/Cdnfsd_Core.php:48 Stack trace: #0 /PATH/TO/FOLDER/wp-content/plugins/w3-total-cache/Cdnfsd_CacheFlush.php(222): W3TC\Cdnfsd_Core->get_engine() #1 /PATH/TO/FOLDER/wp-includes/class-wp-hook.php(286): W3TC\Cdnfsd_CacheFlush::w3tc_flush_execute_delayed_operations(Array) #2 /PATH/TO/FOLDER/wp-includes/plugin.php(203): WP_Hook->apply_filters(Array, Array) #3 /PATH/TO/FOLDER/wp-content/plugins/w3-total-cache/CacheFlush_Locally.php(253): apply_filters(‘w3tc_flush_exec…’, Array) #4 /PATH/TO/FOLDER/wp-content/plugins/w3-total-cache/CacheFlush.php(188): W3TC\CacheFlush_Locally->execute_delayed_operations() #5 /PATH/TO/FOLDER/wp-content/plugins/w3-total-cache/CacheFlush.php(194): W3TC\CacheFlush->execute_delayed_operations() #6 /PATH/TO/FOLDER/wp-includes/class-wp-hook.php(288): W3TC\CacheFlush->execute_delayed_operations_filter(‘https://www.yourdomain…’) #7 /PATH/ in /PATH/TO/FOLDER/wp-content/plugins/w3-total-cache/Cdnfsd_Core.php on line 48/

The issue is caused by a new feature called FSD CDN that has been available in the latest W3 Total Cache version (0.9.6). FSD (Full Site Delivery) is a feature that helps reduce page load time, and seemingly loads your website instantly for visitors.

W3 Total Cache uncaught Exception Unknown Engine 500 Fatal Error FSD CDN For some non apparent reason (that’s a fancy way of saying it’s a bug), the FSD CDN feature in W3TC is enabled and activated by default. The FSD CDN type is locked onto CloudFlare (other types are Amazon CloudFront, Limelight and MaxCDN) as the FSD CDN service provider, The FSD CDN option is General Settings of W3 Total Cache is grayed out and disabled though. Thus, to resolve the issue, SSH into the web server, and edit the ..wp-content/w3tc-config/master.php file.
Search for the the section for cdnfsd, and set the cdnfsd.enabled to “0” or FALSE.even though this feature is only available after upgrade.

The FSD CDN option in General Settings of W3 Total Cache is grayed out and disabled though. To resolve the issue, SSH into the web server or use your control panels file managers, and edit the /wp-content/w3tc-config/master.php file.

Search for the the section for cdnfsd, and set the cdnfsd.enabled to “0” or FALSE.

“cdnfsd.enabled”: “0”,
“cdnfsd.engine”: “”,
“cdnfsd.debug”: false,

Now all we need to do is save the master.php file and the error is fixed!

Of course if you don’t feel comfortable with editing this little 1 to 0 you can always just hang tight and wait for the guys over at W3 Total Cache to fix it. I’m sure that will get it done with the next update.

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