I also encountered this problem,
I add new bundle namespace in composer.json
"autoload": { "psr-4": { "AppBundle\\": "src/AppBundle", "BlogBundle\\": "src/BlogBundle" }, "classmap": [ "app/AppKernel.php", "app/AppCache.php" ] },
and then,
cmd $ composer dump-autoload.//如报ssh错,则修改php.ini ，开户open_ssh
the issue is settled