When I refresh the page it duplicates a image

on my webs , only admin can log in so it should be fairly foolproof ...however
i use a form to upload an image

i get data on image name such as ..

Code:

$file = $this->request->getFile('userfile');
                   $name= $file->getName();
                $tempfile = $file->getTempName();
                $slug= url_title($cleanTitle);

but before any image can be uploaded i do a check on directory where irt would go, using variations on:

Code:

file_exists(nameOfImage)

So if there was refresh or any circumstance where there was an attempt to load same image, it would feedback "image already exists" so it would do that before
any image was uploaded

CMS CI4     I use Arch Linux by the way