php bin / console symfony命令给出致命错误

Question

I installed a symfony 3 project but cant run any php bin/console commands. When I try, I get the following error:

PHP Fatal error: Uncaught Symfony\Component\Debug\Exception\ClassNotFoundException: Attempted to load class "DOMDocument" from the global namespace. Did you forget a "use" statement? in project_folder/vendor/symfony/symfony/src/Symfony/Component/Config/Util/XmlUtils.php:52

Any idea how to fix this?