Laravel5.6 Illuminate\Encryption\Encrypter 加密的 key 是什么啊 ???

你好，在EncryptionServiceProvider服务提供者的注册方法中说明，加密所用的key即为php artisan key:generate命令生成的保存在.env文件中的APP_KEY：

public function register()
    {
        $this->app->singleton('encrypter', function ($app) {
            $config = $app->make('config')->get('app');

            // If the key starts with "base64:", we will need to decode the key before handing
            // it off to the encrypter. Keys may be base-64 encoded for presentation and we
            // want to make sure to convert them back to the raw bytes before encrypting.
            if (Str::startsWith($key = $this->key($config), 'base64:')) {
                $key = base64_decode(substr($key, 7));
            }

            return new Encrypter($key, $config['cipher']);
        });
    }