laravel 安装有点小问题（the requested PHP extension fileinfo is missing from your system.）

Problem 1
- Installation request for league/flysystem 1.0.47 -> satisfiable by league/flysystem[1.0.47].
- league/flysystem 1.0.47 requires ext-fileinfo * -> the requested PHP extension fileinfo is missing from your system.
Problem 2
- league/flysystem 1.0.47 requires ext-fileinfo * -> the requested PHP extension fileinfo is missing from your system.
- laravel/framework v5.7.9 requires league/flysystem ^1.0.8 -> satisfiable by league/flysystem[1.0.47].
- Installation request for laravel/framework v5.7.9 -> satisfiable by laravel/framework[v5.7.9].

To enable extensions, verify that they are enabled in your .ini files:
- D:\phpStudy\PHPTutorial\php\php-7.2.1-nts\php.ini
You can also run `php --ini` inside terminal to see which files are used by PHP in CLI mode.
Application ready! Build something amazing.

出现此错误的原因是php.ini中的fileinfo扩展没有开启，开启 extension=php_fileinfo.dll，再重新执行命令安装就可以了。