thinkphp 5 can be used to start the installation composer
So before installing thinkphp5.1, we install the composer, Download: https://www.phpcomposer.com/
After installing the composer, at the command line:composer create-project topthink/think=5.1.* tp5 等待下载完，think=5.1.*框架thinkphp的版本
If the original is already installed thinkphp5.0, usecomposer update topthink/framework进行更新安装
View tp version number:
use App ;
var_dump(App:version()) ;