Slider Revolution Fatal Error


My client reported they were unable to access their site wp-admin, i checked and it said there was a critical error on the site and it would not show the wordpress login page. I accessed the site via ftp and renamed the plugins and eventually worked out it was slider revolution which was causing admin to not be accessible even though on the front end of the site it appeared to be working ok. I have checked and I am getting the following fatal error:

Plugin could not be activated because it triggered a fatal error.

Just to note, I have the latest version of Wordpress, X-theme and PHP running on the server

Any ideas?

Hey @appletreeweb,

This could be a conflict with a feature of PHP. Would you mind downgrading to PHP 7 and if that doesn’t help, try PHP 5.6. If changing PHP version works, your web host need to find what PHP feature is conflicting with Slider Revolution. I have PHP 7.4 in my test site but Slider Revolution works so it’s “generally” compatible with the latest PHP version.

After testing the PHP version and that does not help, please copy your live site to a staging server and give us the Staging WordPress Admin and FTP login details in a Secure Note

If you don’t want to set up staging, we can investigate in your live site but please note that troubleshooting in your live site carries a risk of breaking it. We also need to disable all third-party plugins so that could disrupt your live site’s operation.


Hi, thanks for your reply. I have switched the php back to the outdated 7.0.33 and this has allowed the plugin to be activated and the slider runs however I am concerned the site is now running on an outdated version of PHP which is a security risk. The site is not running that many plugins:

wp-plugins-active (8)

Implied Cookie Consent: version: 1.3, author: Stefan Senk
Revolution Slider: version: 4.6.5, author: ThemePunch
Smash Balloon Custom Facebook Feed: version: 2.12.3, author: Smash Balloon
Visual Composer: version: 24.0, author:
WordPress DBCache: version: 3.2.8, author:
WordPress SEO Tools: version: 2.2.5, author:
WPBakery Visual Composer: version: 4.3.5, author: Michael M -
X – Shortcodes: version: 3.0.5, author: Themeco

Hey @appletreeweb,

I understand your concern. However, it is the web host’s PHP configuration that is conflicting with Slider Revolution.

Thank you for understanding.

The php settings are standard. Nothing is configured differently and I have never had any issues with other plugins not working on any other website hosted on the same server

Hello @appletreeweb,

Would you mind providing us access to your site so that we can check your settings. Please create a secure note with the following info:
– Link to your site
– WordPress Admin username / password

To know how to create a secure note, please check this out:

Thank you in advance.


I have been checking with my hosting company and they have confirmed the PHP is a standard config. I sent them the error I receive and they have said the issue is the the compatibility of the PHP code for the latest PHP versions, see following:

The actual issue is caused by the PHP version. Prior to 7.1.0, code similar to the following:

$str[] = ‘something’ - would work, because PHP would convert the empty [] silently into an array.

7.1.0 and later require the array to be initialised before assigning it.

$str = [];
$str[] = 'something

This is noted in the incompatible changes in the PHP 7.1 changes document.

Hi @appletreeweb,

Is your site really running these plugins version?

Most of these plugins are outdated while your Wordpress is up to date, so yeah it is likely that you’ll be going to encounter incompatibility issues with these outdated plugins, I think this was the culprit why your Revolution Slider is suddenly causing Fatal error, yes PHP version is possible to be in play as well because we can agree that some of those plugin versions developed before PHP 7.0 or higher.

You have two options here, either you restore your Wordpress version to date was it still working fine, or if you know what version of Wordpress exactly you have before the Wordpress updated to the latest version, then you can downgrade your Wordpress to that version, and then keep everything outdating if that’s what you like. You can follow this guide here to disable the WordPress automatic update.

Or you update everything to the latest version (Wordpress, Theme, X - Shortcode to Cornerstone, all plugins), this might take you time though since you’re coming from a very old version and might break a few minor things.

Remember to clear all your caching features (plugin, server-side, CDN, and browser’s cache) after updating so that the code from the latest release is always in use. This will help you to avoid any potential errors.


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