Laravel project creation, Your requirements could not be resolved to an installable set of packages

I'm trying to create a project using a composer. I use the following command. My folder consist of another project but in a separate folder.

composer create-project --prefer-dist laravel/laravel blog

The error I get is,

Your requirements could not be resolved to an installable set of packages.

Some answers in Stackoverflow says to upgrade the PHP. But in my case it's already updated to newest version. php -v says,

Is there any solution? Any suggestion is warmly welcome.

via Chebli Mohamed