1.php版本需要5.5.9+
2.安装composer
3.下载laravel
打开cmd，进入需要下载的目录，执行如下Composer命令：
composer create-project laravel/laravel --prefer-dist
该过程可能报以下错误：
Failed to enable crypto
failed to open stream: operation failed
需要更换composer镜像源：
更换成阿里镜像：
composer config -g repo.packagist composer https://mirrors.aliyun.com/composer/
更换成Laravel China镜像：
composer config -g repo.packagist composer https://packagist.laravel-china.org
更换成中国全量镜像：
composer config -g repo.packagist composer https://packagist.phpcomposer.com
即可在该目录中安装一个目录名的laravel的新的Laravel应用，如果你想指定自定义的安装目录名，如laravelapp，则使用如下命令即可：
composer create-project laravel/laravel laravelapp --prefer-dist
如果安装过程中报错：
[RuntimeException]
Could not load package classpreloader/classpreloader in http://packagist.org: [UnexpectedValueException] Could not parse version constraint ^1.2.2: Invalid version string "^1.2.2"
则表示需要更新Composer：
composer self-update
