6.Composer实现PHP中类的自动加载

{
    "require": {
        "slim/slim": "^3.9"
    },
    "autoload": {
        "psr-4": {
            "App\\": "app/"
        }
    }
}

composer dump-autoload  // 更新后运行这个命令

https://www.cnblogs.com/yue-blog/p/5904275.html   // composer 加载自己的类

http://blog.youkuaiyun.com/keyunq/article/details/54773292

https://segmentfault.com/a/1190000010832055