Fatal Error on start

Please help about: Fatal error : Cannot declare interface Psr\Container\ContainerInterface, because the name is already in use in /home/crmeurogalvano/www/vendor/psr/container/src/ContainerInterface.php on line 10

Are you using composer?

I’ve seen this error before but in a different project - It was using a cached version of the file and as 2 files exist there’s a conflict in whatever it’s trying to do.