Prevent Double Form Submission + Error Message

[Foxie]

Hello! I am new here, so i hope i dont make any mistakes when it comes to rules here on the forums

But i am really devastated at the moment. For an assignment of mine, i already wrote a normform. But now, the task is that i prevent the double submit when the page is refreshed, and show an error message that the uploaded file (for thats the normform for) was already submitted. 

I simply am not able to do it!

 

So far i managed to prevent the double submission. I can now refresh the page and it does not upload the file again. I made this possible by redirecting to my own page after the process form function is called, so that the POST is transformed into a GET request. But i simply cannot make the message show up.

 

This is my code i have so far for this:

 protected function business()
        {
            if (isset($_SESSION['number']) && isset($_POST['number'])) {
                if ($_POST['number'] == $_SESSION['number']) {

                    unset($_SESSION['token']);

                    if ($this->addImage()) {

                        header("Location: " . $_SERVER['REQUEST_URI']);
                        //exit();

                        $this->statusMessage = "Your file has been uploaded successfully";
                        $this->currentView->setParameter(new GenericParameter("statusMessage", $this->statusMessage));
                        $this->currentView->setParameter(new GenericParameter("images", $this->getImages()));
                        $this->currentView->setParameter(new PostParameter(IMAR::IMAGE_TITLE, true));
                        $this->currentView->setParameter(new PostParameter(IMAR::IMAGE_AUTHOR, true));

                        $_SESSION["number"] = 0;

                        unset($_POST);

                        echo "Test";

                        // redirecting to the same page - makes a get out of the post and prevents
                        // the double upload / the window to confirm to upload it again





                    } else {

                        echo "Test2";
                        $this->errorMessages ["addImage"] = "Error adding image. Please try again";
                    }

                } else {

                    echo "Test 3";
                    $_SESSION["number"] = 2;

                }
            }

And this is my vaidation method. Here the error messages should be generated:

  if ($_SESSION["number"] == 2) {
           echo "Hallo";
           $this->errorMessages[self::IMAGE_UPLOAD] = "File already submitted!";
       }

       if (!isset($_POST)) {
           echo "Hallo2";
           $this->errorMessages[self::IMAGE_UPLOAD] = "File already submitted!";
       }

        // ----------------------------------

        $this->currentView->setParameter(new GenericParameter("errorMessages", $this->errorMessages));

        return (count($this->errorMessages) === 0); 

Can somebody PLEASE tell me what i am doing wrong?? I am sitting at this for three days now. I have only been learning php for 3 months now, and i am simply on the edge of pure frustration

 

Love, Foxie

[Jacques1]

I'm not even sure what you are trying to do.

 

If you don't want people to upload the same file, then you obviously need a duplicate check for those files -- based on the filename, a checksum of the content or whatever. Playing with sessions doesn't help, because the user could completely log out and then come back with the same file again -- or does that make it acceptable?

 

The solution to your problem (as I understand it) is to come up with unique identifiers for the files (name, checksum, ...), store those identifiers in a database and show an error message when you encounter a duplicate. The easiest and safest uniqueness check is to use a real database system (PostgreSQL, MySQL, SQLite, whatever) which can perform the check by itself. Then you just have to catch the error and show your own message.