Can only install one of: topthink/think-installer[v2.0.0, v1.0.12].

• 這種情況發生在:
  我要在自己的 ThinkPHP5.1.2框架中，使用 composer 命令安裝 workerMan 拓展的時候所提示的信息

• composer 命令：composer require topthink/think-worker=v2.0.9

• 提示信息
  

• 打印信息如下：

./composer.json has been updated
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
    - Can only install one of: topthink/think-installer[v2.0.0, v1.0.12].
    - Can only install one of: topthink/think-installer[v2.0.0, v1.0.12].
    - Can only install one of: topthink/think-installer[v2.0.0, v1.0.12].
    - topthink/think-worker v2.0.9 requires topthink/think-installer ^2.0 -> satisfiable by topthink/think-installer[v2.0.0].
    - Installation request for topthink/think-worker v2.0.9 -> satisfiable by topthink/think-worker[v2.0.9].
    - Installation request for topthink/think-installer (locked at v1.0.12) -> satisfiable by topthink/think-installer[v1.0.12].


Installation failed, reverting ./composer.json to its original content.

• 通過對提示信息的閱讀理解，說明當前的框架只讓安裝 v2.0.0, v1.0.12 的其中一個;
  也就是說，當前的 ThinkPHP 框架太低，不足以滿足 v2.0.9 版本的 workerMan;
  解決方案就是： 安裝一個較低版本的 workerMan唄！