How to protect HTML form from blank submission

Question

Basically I\'m using this tutorial: HTML FORM

Everything is working as it should but one flow I\'ve found is that everyone can see the URL for your

Answer 1

First you can use the required attribute on mandatory fields for client-side:

But you will need to verify server-side in case the user modified the form. You can use empty() on any variable ($_POST or $_GET):

if (empty($_POST['mandatory_field'])) {
    // print error message or redirect to form page
}

You can use isset() to verify if a field is submitted. Your validation could be:

if (!isset($_POST['mandatory_field']) || empty($_POST['mandatory_field'])) {
    // print error message or redirect to form page
}

---

Other cases:
If all fields are mandatory you could check with in_array():

if (in_array(false, $_POST)) {
    // print error message or redirect to form page
}

If doing various data validation here is what I use to do with forms:

$errors = [
    'empty field'           => empty($_POST['field']),
    'another error message' => $another_condition
];

if (in_array(true, $errors)) {
    $error_message = array_search(true, $errors);
    // print or redirect, and you can tell the user what is wrong
}