Could not fetch https://api.github.com/repos/... please create a GitHub OAuth token to go over the API rate limit
Head to https://github.com/settings/t...
to retrieve a token. It will be stored in "C:/Users/Administrator/AppData/Roaming/Composer/auth.json" for future use by Composer.
为了安装yii2,你自己必须先要有一个github账号,然后用你自己的github账号生成的token来安装,说明已经很清楚了,按照说明,点击第二个链接生成token后接着安装。