Download file does not exist - symfony

Question

I build a csv export using the admin folder. The file is well uploaded into my public folder.
But when I try to download it using the return, I have an error:
The file "/public/exportCSV.csv" does not exist
I can't understand why, I hope you have an idea. Thanks. I'm under Symfony 4.
$admins = $userRepository->findByRole(User::ROLE_ADMIN);
$filename='exportCSV';
$extension='csv';
$request = Request::createFromGlobals();
if($request->query->get('exportCSV')!= null){
$output = fopen($filename.'.'.$extension, 'w');
fputcsv($output, array("Id","Nom","Prénom","Activé","Dernière connexion","Date d'inscription","Url avatar","Email","Username"));
foreach ($admins as $admin){
$id=$admin->getId();
$lastname=$admin->getLastName();
$firstname=$admin->getFirstName();
$activeState=$admin->getActiveState();
if($activeState){
$active='Oui';
}else{
$active='Non';
}
$lastConnectedAt=$admin->getLastConnected();
if($lastConnectedAt==null){
$lastConnected=" ";
}else{
$lastConnected=$lastConnectedAt->format('Y-m-d H:i:s');
}
$createdAt=$admin->getCreatedAt();
if($createdAt==null){
$created=" ";
}else{
$created=$createdAt->format('Y-m-d H:i:s');
}
$urlAvatar=$admin->getUrlAvatar();
$mail=$admin->getEmail();
$username=$admin->getUsername();
$csvLine= array($id,$lastname,$firstname,$active,$lastConnected,$created,$urlAvatar,$mail,$username);
fputcsv($output,$csvLine);
}
return $this->file('/public/'.$filename.'.'.$extension);
}

Answer 1

You must use the correct path to webserver "public" dir. Check https://stackoverflow.com/a/48585423/3497902
In your example, you can do same like ...
$publicDir = $this->getParameter('kernel.project_dir') . '/public/'; # Your controller must extend AbstractController
$output = fopen($publicDir . $filename.'.'.$extension, 'w');