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Troubleshooting W3 Total Cache Issues

This tutorial is part of a series relating to W3 Total Cache. This part of the series deals with troubleshooting W3 Total Cache Errors.

This tutorial is part of a series relating to W3 Total Cache. This part of the series deals with troubleshooting W3 Total Cache Errors.

In this part of the series, we will look at the following:

  1. W3 Total Cache Installation Problems
  2. General Troubleshooting

The post is a work in progress, and more problems \ solutions be added as the W3 Total Cache Series is completed (due to be finished by the end of 2016)

W3 Total Cache Installation Problems

Occasionally when installing W3 Total Cache, you may run into some issues, especially if you have not carried out our pre-installation checks mentioned in Step 1 above. We have highlighted some of the common problems people face below:

Error: advanced-cache.php is not installed

Error Message"Page caching is not available: advanced-cache.php is not installed. Either the /home/content/92/7450992/html/wp-content directory is not writable, or you have another caching plugin installed. This error message will automatically disappear once the change is successfully made."

Solution: You need to remove completely any other caching plugin before you install W3 Total Cache. You need to remove W3 Total Cache and undertake the checks in Step 1 above before proceeding:

  • Deactivate and DELETE any other caching plugin. Make sure you check the wp-content directory and delete the advanced-cache.php file, object-cache.php and the db.php file.
  • Deactivate and DELETE W3 Total Cache.
  • Reinstall the plugin and activate.

Error: W3 Total Cache Not Working on Multisite install

Error MessageWP admin showed only a title page Dashboard

Solution: Make sure that the Multisite Admin website has W3TC configured. On the Performance -> General Settings Tab uncheck "Use single network configuration file for all sites".

Error: PHP Fatal error

Error Message: PHP Fatal error: Call to undefined function get_home_url() in /home5/felicetr/public_html/labbondanzavienedalcuore/wp-content/plugins/w3-total-cache/inc/define.php on line 617

Solution: Delete the plugin via SSH or File Manager. You can follow Step 1 above to delete the relevant .htaccess code, and other specified files. In addition delete the /wp-content/cache/ folder, the /wp-content/plugins/w3-total-cache/ folder. You should now be able to access your site's admin area, and reinstall W3 Total cache.

General Troubleshooting

"I am having display issues after updating other plugins \ themes on my website. W3 Total Cache was working fine before."

It's likely the plugin author may have modified their JS or CSS in the new release, but the old versions are being served from cache. Clear the cache, and any CDN cache (if applicable). Sometimes, updated plugins \ themes can introduce duplicate code which may have caused a conflict. If this is the case, you may need to revisit your minification settings.

"I see garbage characters instead of the normal website, what's going on here?"

If a theme or it's files use the call php_flush() or function flush() that will interfere with the plugins normal operation; making the plugin send cached files before essential operations have finished. The flush() call is no longer necessary and should be removed.

"I'm getting blank pages or 500 error codes when trying to upgrade on WordPress MU"

First, make sure the plugin is not active (disabled) network-wide. Then make sure it's deactivated network-wide. Now you should be able to successful upgrade without breaking your website.

"My YSlow score is low because it doesn't recognize my CDN, what can I do?"

Rule 2 says to use a content delivery network (CDN). The score for this rule is computed by checking the hostname of each component against the list of known CDNs. Unfortunately, the list of "known CDNs" are the ones used by Yahoo! Most likely these are not relevant to your website, except for potentially yui.yahooapis.com. If you want an accurate score for your website, you can add your CDN hostnames to YSlow using Firefox's preferences. Here are the steps to follow:

  • Go to "about:config" in Firefox. You'll see the current list of preferences.
  • Right-click in the window and choose New and String to create a new string preference.
  • Enter extensions.yslow.cdnHostnames for the preference name.
  • For the string value, enter the hostname of your CDN, for example, mycdn.com. Do not use quotes. If you have multiple CDN hostnames, separate them with commas.

If you specify CDN hostnames in your preferences, they'll be shown under the details for Rule 2 in the Performance view.

"When I post / like my posts on Facebook the wrong text or no images are shown on Facebook."

If this happens you need to add the following user agents to the text area "Rejected user agents" the Page Cache settings page:

facebookexternalhitFacebookExternalHit/1.1FacebookExternalHit/1.0

Also, make sure you have the correct xmlns:og /xmlns:fb tags in your opening HTML tag.

"The plugin tells me to add w3tc-wp-loader.php but minify loads correctly?"

If you put the symlink path in w3tc-wp-loader.php the plugin will think the path has changed because WordPress converts symlinks to realpath. You can disable the check by adding the following to your wp-config.php.:

define('DONOTVERIFY_WP_LOADER', true);

"A notification about file owner appears along with an FTP form, how can I resolve this?"

The plugin uses WordPress FileSystem functionality to write to files. It verifies that file owner, file owner group of created files match process owner. If this is not the case, it cannot write or modify files.

Typically, you should ask your web host about the permissions issue, and they should be able to resolve it. You can, however, try adding the following code to your wp-config.php to circumvent the file and folder checks.

define('FS_METHOD', 'direct'); 

I get an CloudFlare error message similar to "certificate verify locations: CAfile: /etc/path/certs/ca-bundle.crt CApath: none"

This is an issue relating to your SSL certificate. It could be that they are stored in the incorrect location, or that they do not have the correct permissions. You should refer this to your web hosting provider to fix.

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