楼主帮忙看看，我composer install的时候下图报错：
[root@VM_0_14_redhat yii2admin]# composer install
Loading composer repositories with package information
Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.

Problem 1

- yiisoft/yii2 2.0.x-dev requires bower-asset/punycode 1.3.* -> no matching package found.
- yiisoft/yii2 2.0.15.1 requires bower-asset/jquery 3.2.*@stable | 3.1.*@stable | 2.2.*@stable | 2.1.*@stable | 1.11.*@stable | 1.12.*@stable -> no matching package found.
- yiisoft/yii2 2.0.15 requires bower-asset/jquery 3.2.*@stable | 3.1.*@stable | 2.2.*@stable | 2.1.*@stable | 1.11.*@stable | 1.12.*@stable -> no matching package found.
- yiisoft/yii2 2.0.14.2 requires bower-asset/jquery 3.2.*@stable | 3.1.*@stable | 2.2.*@stable | 2.1.*@stable | 1.11.*@stable | 1.12.*@stable -> no matching package found.
- yiisoft/yii2 2.0.14.1 requires bower-asset/jquery 3.2.*@stable | 3.1.*@stable | 2.2.*@stable | 2.1.*@stable | 1.11.*@stable | 1.12.*@stable -> no matching package found.
- yiisoft/yii2 2.0.14 requires bower-asset/jquery 3.2.*@stable | 3.1.*@stable | 2.2.*@stable | 2.1.*@stable | 1.11.*@stable | 1.12.*@stable -> no matching package found.
- Installation request for yiisoft/yii2 ~2.0.14 -> satisfiable by yiisoft/yii2[2.0.14, 2.0.14.1, 2.0.14.2, 2.0.15, 2.0.15.1, 2.0.x-dev].

Potential causes:

• A typo in the package name
• The package is not available in a stable-enough version according to your minimum-stability setting
  see https://getcomposer.org/doc/04-schema.md#minimum-stability for more details.
• It's a private package and you forgot to add a custom repository to find it

Read https://getcomposer.org/doc/articles/troubleshooting.md for further common problems.

我下载下来没有vendor这个目录，我从官网初始版本copy了一个过来，现在运行有一个undefined function env()，详情见下：

Fatal error: Uncaught Error: Call to undefined function env() in D:\phpStudy\PHPTutorial\WWW\admin.phpdamon.cn\common\config\bootstrap.php:25 Stack trace: #0 D:\phpStudy\PHPTutorial\WWW\admin.phpdamon.cn\backend\web\index.php(14): require() #1 {main} thrown in D:\phpStudy\PHPTutorial\WWW\admin.phpdamon.cn\common\config\bootstrap.php on line 25