Fatal error: Uncaught Error: Class 'yii\db\Migration' not found in /var/www/html/autocar/migrations/m200904_143927_add_main_to_attr_tbl.php:8 Stack trace: #0 {main} thrown in /var/www/html/autocar/migrations/m200904_143927_add_main_to_attr_tbl.php on line 8