yii2连接数据库失败

 public function actionIndex()
 {
 $query = Country::find();
 
 $pagination = new Pagination([
 'defaultPageSize' => 5,
 'totalCount' => $query->count()
 ]);
 
 $countries = $query->orderBy('name')
 ->offset($pagination->offset)
 ->limit($pagination->limit)
 ->all();
 
 return $this->render('index', [
 'countries' => $countries,
 'pagination' => $pagination,
 ]);
 }

<?php
 
return [
 'class' => 'yiidbConnection',
 'dsn' => 'mysql:host=localhost;dbname=yii2basic',
 'username' => 'root',
 'password' => '',
 'charset' => 'utf8',
 
 // Schema cache options (for production environment)
 //'enableSchemaCache' => true,
 //'schemaCacheDuration' => 60,
 //'schemaCache' => 'cache',
];

<?php
 
return [
 'class' => 'yiidbConnection',
 'dsn' => 'mysql:host=127.0.0.1;dbname=yii2basic',
 'username' => 'root',
 'password' => '',
 'charset' => 'utf8',
 
 // Schema cache options (for production environment)
 //'enableSchemaCache' => true,
 //'schemaCacheDuration' => 60,
 //'schemaCache' => 'cache',
];