这个是另一个package，你说的“自己实现”，其实也对的，这个地方也可以放你自己定义的class

其实这段代码产生的效果是

比如

$this->app->singleton('ReportServices', function () {
    return new \App\Services\ReportServices();
});

以后在其他class里我可以用

app('ReportServices')->xxxxxx();

去代替

$services = new \App\Services\ReportServices();
$services->xxxxxx();

Providers的存在目的就是在程序启动的时候注册各种东西，比如你要扩展Cache类去使用阿里云ocs

public function boot()
    {
        //扩展阿里云OCS缓存
        Cache::extend('ocs', function ($app, $config) {
            $prefix = $app['config']['cache.prefix'];
            $memcached = new \Memcached;
            foreach ($config['servers'] as $server) {
                $memcached->addServer(
                    $server['host'], $server['port'], $server['weight']
                );
                if (ini_get('memcached.use_sasl')) {
                    $user = $server['authname'];
                    $pass = $server['authpass'];

                    $memcached->setOption(\Memcached::OPT_COMPRESSION, false);
                    $memcached->setOption(\Memcached::OPT_BINARY_PROTOCOL, true);
                    $memcached->setSaslAuthData($user, $pass);
                }
            }
            $store = new \Illuminate\Cache\MemcachedStore($memcached, $prefix);

            return new \Illuminate\Cache\Repository($store);
        });
}

比如你要扩展表单验证类

public function boot()
{
    //扩展表单验证
        Validator::extend('greater_than', function ($attribute, $value, $parameters)     
        {
            $other = Request::input($parameters[0]);

            return isset($other) && intval($value) > intval($other);
        });
}