I've always started new Symfony projects with Composer executing:
composer create-project symfony/framework-standard-edition my_project_name
until now..
For no apparent reason, Composer started to complain with this error:
Class SymfonyStandard\Composer is not autoloadable, can not call post-root-package-install script
Has anyone encountered this problem?
I should also add that Composer proceeded with installing the project after displaying this message.
Try removing your vendor directory and trying again with your curl extension enabled correctly.