PHP delete values from the form if successful

Question

I would like the values of this form to be deleted if the form is successfully submitted, everything is ok (does not erase) if there is any error but if there are no values continue there, I believe it is a logical error.

    <form action="" method="POST" enctype="multipart/form-data">
    <label>Image<br><input type="file" name="file"></label><br><br>
    <label>Name for the image<br><input type="nameImg" name="imgName" value ="<?php if (!empty($_POST['imgName'])) { echo $_POST['imgName']; } else if (empty($database->errors())) { echo ''; } ?>"></label><br><br>
    <label>Link you wish it to have<br><input type="text" name="imgLink" value ="<?php if (!empty($_POST['imgLink'])) { echo $_POST['imgLink']; } else if (empty($database->errors())) { echo ''; } ?>"></label>
    <br>
    <input type="submit" value ="Upload Image">
</form>
<?php
if (isset($_POST['imgLink'], $_POST['imgName'], $_FILES['file']['name'])) {

    $imgName = htmlentities('\'' .$_POST['imgName']. '\''); //Because of this $imgName will never be empty, we have to pass the pure input to imageInputCheck($_POST['imgName'])
    $link = htmlentities($_POST['imgLink']);

    $name = htmlentities($_FILES['file']['name']);

    $temp = explode('.', $name);
    $file_extn = strtolower(end($temp));

    $tmp_name = $_FILES['file']['tmp_name'];
    $path = "images/" .uniqid('', true). '.' .$file_extn;



    if ($database->imageInputCheck($link, $_POST['imgName'], $name, $file_extn)) {
        $database->insertFolder($tmp_name, $path);
        $database->insertDB($path, $link, $imgName);
        echo '<br>Image upload successful.';
    }
    else {
        foreach ($database->errors() as $error) {
            echo '<div id="errors">' .$error. '</div>';
        }
    }
}

DB.php

protected $_errors = [];

public function imageInputCheck($link, $imgName, $name, $file_extn) {

        if (empty($link) && empty($name) && empty($_POST['imgName'])) {
            $this->addError('<br>Fill all<br>Don\'t be stupid');
        }
        else if (empty($link) || empty($name) || empty($_POST['imgName'])) {
            $this->addError('<br>You forgot to:<br><br>');
            if (empty($name)) {
                $this->addError('Upload an image');
            }
            if (empty($_POST['imgName'])) {
                $this->addError('Give a name to your image');
            }
            if (empty($link)) {
                $this->addError('Give a link to your image');
            }
        }

        else if (($file_extn == 'jpg' || $file_extn == 'png' || $file_extn == 'tif' || $file_extn == 'gif' || $file_extn == 'jpeg') && strlen($imgName) <= 60) {
            return true;
        }
        else {
            $this->addError('<br>Couldn\'t upload file to database or the folder, make sure it\'s an image.<br>Make sure it\'s name is under 60 characters');
        }
        return false;
    }

private function addError($error) {
        $this->_errors[] = $error;
    }

    public function errors() {
        return $this->_errors;
    }

Answer 1

In PHP, there is no effective way to unset $_POST as a whole. You can even unset the keys you used, for example:

unset($_POST['imgName']);
unset($_POST['imgLink']);
...

But anyway, the only effective and secure solution is to resend the page, or better yet, perform the processing in a separate file (indicated in the "action" parameter of the tag form) and redirect back to the page at the end....

header('location:caminho/pagina-de-volta.php');

In case of errors, you can use sessions or query strings to signal the problem, retrieve values in the form, etc.

Answer 2

Dear Miguel, I think it is relevant to eliminate the logic of Html, separating into different things:

<?php
$imgName = isset($_POST['imgName']) ? $_POST['imgName'] : ""; 
$imgLink = isset($_POST['imgLink']) ? $_POST['imgLink'] : "";
?>

<form action="" method="POST" enctype="multipart/form-data">
    <label for="file">Image<br></label>
    <input type="file" name="file">
    <br><br>
    <label for='nameImg'>Name for the image</label>
    <input type="nameImg" name="imgName" value ="<?php echo $imgName ?>">
    <br><br>
    <label for="imgLink">Link you wish it to have</label><br>
    <input type="text" name="imgLink" value ="<?php echo $imgLink ?>">
    <br>
    <input type="submit" value ="Upload Image">
</form>

And within the bond that validates and saves:

if ($database->imageInputCheck($link, $_POST['imgName'], $name, $file_extn)) {
    $database->insertFolder($tmp_name, $path);
    $database->insertDB($path, $link, $imgName);
    unset($_POST);
    echo '<br>Image upload successful.';
}

If all is right, it will delete the post variables, and when you return to the form, the conditional assignments will set the values with " ".