A Magento website was down with following error. Fatal error: Uncaught Error: Class 'DOMDocument' not found in /home/bunnytech/public_html/vendor/magento/framework/Config/Dom.php:390 Stack trace: #0 /home/bunnytech/public_html/vendor/magento/framework/Config/Dom.php(117): Magento\Framework\Config\Dom->_initDom('<?xml version="...') The issue was that php xml module was not installed/enabled. "DOM/XML" should be in enabled state while accessing the php info page.