修改数据库编码格式

@@ -28,7 +28,7 @@ return [
             'dsn' => 'mysql:host=10.66.1.219;port=3306;dbname=yh_live',
             'username' => 'root',
             'password' => 'yoho@Uniformpass',
-            'charset' => 'utf8',
+            'charset' => 'utf8mb4',
             'tablePrefix'=>'tbl_',
             'schemaCache' => 'pageCache',
             'queryCache' => 'pageCache',