yii\web\Request::cookieValidationKey must be configured with a secret key.

参考：​​http://www.yiiframework.com/forum/index.php/topic/56238-cookievalidationkey-must-be-configured-with-a-secret-key/​​

我的yii2模板是：yii-basic-app-2.0.9.tgz

解压后执行命令：yii serve --port=8888

访问：http://localhost:8888/

出现如下错误：

Invalid Configuration – yii\base\InvalidConfigException

 yii\web\Request::cookieValidationKey must be configured with a secret key.----------------------------------------------------------------------------------------------------------------
解决方法：
打开文件config\web.php, 设置 'cookieValidationKey' => 'true',即可，如;
$config = [
     'id' => 'basic',
     'basePath' => dirname(__DIR__),
     'bootstrap' => ['log'],
     'components' => [
         'request' => [
             // !!! insert a secret key in the following (if it is empty) - this is required by cookie validation
             'cookieValidationKey' => 'true',     //  就是这里了
         ],
         'cache' => [
             'class' => 'yii\caching\FileCache',
         ],........