Fatal error: Uncaught Error: Class 'yii\db\Migration' not found in /home/wittyly/public_html/live/hr-witty/migrations/m191212_050255_add_threshold_column_to_org_alert_settings_table.php:8 Stack trace: #0 {main} thrown in /home/wittyly/public_html/live/hr-witty/migrations/m191212_050255_add_threshold_column_to_org_alert_settings_table.php on line 8