Yii2 Flash message not appear after redirect

Question

I want to set flash message, but flash message missing if i add redirect. if i remove the line of redirect code then the flash message will be shown, but if i remove the redirect when i click on F5 refresh it will run again the file submission. How to make redirect work together with the flash message?

the flow of my controller like this:

public function actionImportVehiclecsv()
    {
        $model = new CrmImportVehicle();
        $session = Yii::$app->session; // Get the session component
    
        if (Yii::$app->request->isPost) {
            $model->csvVehicleFile = UploadedFile::getInstance($model, 'csvVehicleFile');
            $model->csvAccount = Yii::$app->request->post('CrmImportVehicle')['csvAccount'];
            
            if ($model->csvVehicleFile) {
                if ($filePath = $model->upload()) {
                    $processResult = $model->processVehicleFile($filePath);
                    
                    if ($processResult === true) {
                        $session->setFlash('success', 'CSV file uploaded and data inserted successfully.');
                    } elseif ($processResult === false) {
                        $session->setFlash('error', 'Error in CSV row: Vehicle No or Username cannot be blank');
                    } else {
                        $session->setFlash('error', $processResult); // Set error flash message for other errors
                    }
                    $session->set('processed', true); // Indicate that the form was processed
                } else {
                    $session->setFlash('error', 'Error uploading CSV file.');
                }
            } else {
                $session->setFlash('error', 'No file was uploaded.');
            }
    
            return $this->refresh(); // if i  remove this line, the flash message works.
        } elseif ($session->get('processed')) {
            $session->remove('processed'); // Clear the 'processed' flag for GET requests
            return $this->refresh(); // Refresh the page if it was previously processed
        }
    
        // Render the view for GET requests
        return $this->render('import-vehiclecsv', ['model' => $model]);
    }

Flash Message Appear if i remove the line of code

Flash Message missing if i add the refresh line code

Answer 1

The concept of flash messages is in the principle that the message exists only for one request and are then deleted.

I would advise you to check whether you can retain the messages even after a refresh by using the removeAfterAccess parameter.

Source: Yii documentation

Answer 2

$this->refresh() doesnt execute any additional server-side logic. Try using something like $this->redirect(Yii::$app->request->referrer)