yii\db\Migration::down PHP Méthode

    public function down()
    {
        $transaction = $this->db->beginTransaction();
        try {
            if ($this->safeDown() === false) {
                $transaction->rollBack();
                return false;
            }
            $transaction->commit();
        } catch (\Exception $e) {
            echo 'Exception: ' . $e->getMessage() . ' (' . $e->getFile() . ':' . $e->getLine() . ")\n";
            echo $e->getTraceAsString() . "\n";
            $transaction->rollBack();
            return false;
        }
        return null;
    }