PHP8+ errors

Possible error messages

Warning: Private methods cannot be final as they are never overridden by other classes
Warning: The magic method Nextend\Framework\Pattern\SingletonTrait::__wakeup() must have public visibility
Fatal error: Cannot use Nextend\Framework\Form\Element\Mixed as Mixed because 'Mixed' is a special class name

Cause

You are using an old Smart Slider version, which didn't had compatibility codes with PHP 8+ yet.

Solution

Update your Smart Slider.

Try to update it the original way, but if your Smart Slider is too old, that won't work. In that case, do a reinstallation. Your sliders will stay that way too!