How do i fix this error? What cause this error?
Fatal error: Class Magento\Framework\Config\FileIterator contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (Countable::18000) inC:\xampp\htdocs\magento\vendor\magento\framework\Config\FileIterator.php on line 15
Its seem that you created a class and implemented the interface and you doesn't define the function of that interface in implemented class. If you have done this then again re-compile your code. And after re-compile clear cache and give permission to var directory.