可以尝试利用composer下载Yii框架，编辑composer.json文件：
{
"require":{
"yiisoft/yii2":"~2.0.0"
}
}
然后在这个包含composer.json文件的目录下执行命令：
composer install
然后就等待下载完成
问题零：Your requirements could not be resolved to an installable set of packages.
如果出现下面这种情况：
Loading composer repositories with package information Updating dependencies (including require-dev) Your requirements could not be resolved to an installable set of packages.
需要安装一个插件（plug），运行命令安装即可：
composer global require "fxp/composer-asset-plugin:^1.4.1"
问题一：proc_get_status() has been disabled for security reasons
如果出现下面这种情况：
[ErrorException] proc_get_status() has been disabled for security reasons PHP Fatal error: Uncaught exception ‘ErrorException‘ with message ‘proc_get_status() has been disabled for security reasons‘ in phar:///usr/local/bin/composer/vendor/symfony/process/Process.php:1279
这是因为安全原因，将proc_get_status函数禁用了，可以通过编辑php的配置文件php.ini，搜索proc_get_status，将他从disable_functions中删除即可。
问题二：需要输入token
如果是第一次使用composer，那么在下载文件yii框架的过程中，有几项需要输入token，如下图：
[root@localhost tmp]# composer install Loading composer repositories with package information Updating dependencies (including require-dev) Could not fetch https://api.github.com/repos/jquery/jquery-dist, please create a GitHub OAuth token to go over the API rate limit Head to https://github.com/settings/tokens/new?scopes=repo&description=Composer+on+localhost.localdomain+2018-02-22+1945 to retrieve a token. It will be stored in "/root/.composer/auth.json" for future use by Composer. Token (hidden):
只要粘贴上面的URL到浏览器中打开，然后生成一个token，然后复制这个新的token，在命令行中需要token的地方输入该token即可，该token会存储在用户家目录/.composer/auth.json中：
{
"bitbucket-oauth": {},
"github-oauth": {
"github.com": "6ad4ef7375b1fb9........"},
"gitlab-oauth": {},
"gitlab-token": {},
"http-basic": {}
}
此后可以不用再输入token了，composer会自动去auth.json中找。
