I’ve been noticed this Slider Revolution issue in my sites
Fatal error in Slider Revolution 7.x: "class RevSliderAdmin does not have a method add_ajax_footer_functionality"
If you’re seeing this error (in your PHP error log or Query Monitor):
Uncaught Error: call_user_func_array(): Argument #1 ($callback) must be a valid callback, class RevSliderAdmin does not have a method “add_ajax_footer_functionality” in …/class-wp-hook.php
This is a known bug in the Slider Revolution plugin itself, present at least from version 7.1.4 through 7.1.8 (confirmed on multiple separate sites, across different theme versions). It’s not an issue with your setup, theme, or configuration.
Cause: in wp-content/plugins/revslider/admin/revslider-admin.class.php there’s an add_action('admin_footer', ['RevSliderAdmin', 'add_ajax_footer_functionality']) call that hooks a method which no longer exists in the class since the v7 rewrite. The block registering it only runs when the plugin license isn’t validated.
Temporary fix: find that line in the file (line number varies by version, search for it by text) and comment it out:
php
// add_action('admin_footer', ['RevSliderAdmin', 'add_ajax_footer_functionality']);
It gets overwritten on every plugin update, so you’ll need to reapply it after updating. Validating the license may also prevent it from triggering, since the code only runs when unvalidated.