Form submission is not displaying or executing - php

Question

Recently I built a form using HTML, CSS, and JavaScript. I then entered the PHP required to send the data that is inputted in the form, to my database. After I finished, what I thought was necessary for it to work, I ended up with a blank page when I executed the code. The form and everything disappeared. This is my PHP code:
<?php
require("$_SERVER[DOCUMENT_ROOT]/connect.php");
$email = $username = $type = $question = "";
if ($_SERVER["REQUEST_METHOD"] == "POST")
{
if(!empty($_POST))
{
if(isset($_POST["email"], $_POST["username"], $_POST["type"], $_POST["question"])
{
$email = test_input($_POST["email"]);
$username = test_input($_POST["username"]);
$type = test_input($_POST["type"]);
$question = test_input($_POST["question"]);
$premium = ($_POST["premium"]);
$member = $_POST["member"];
$terms = $_POST["terms"];
if ($member != "NO")
{
$member = "YES";
}
}
if(!empty($email) && !empty($username) && !empty($type) && !empty($question) && !empty($terms))
{
$insert = $db->prepare("INSERT INTO QuestionSubmission (Email, Username, Type, Question, Member, Premium, Date) VALUES (?, ?, ?, ?, ?, ?, NOW())");
$insert->bind_param("ssssss", $email, $username, $type, $question, $member, $premium);
if($insert->execute())
{
header("Location: landing.php");
die();
}
}
}
}
function test_input($data)
{
$data = trim($data);
$data = stripslashes($data);
$data = htmlspecialchars($data);
return $data;
}
?>
The "member" part is a check box where the user can optionally select to become a member. It is unchecked initially, and i've set a value of "NO" for that. Also, there is a hidden check box that is already checked with a value of NO...this is the "premium" check box. Lastly, there is a check box for agreeing to the terms. This is initially unchecked, but the user has to check it so it won't be empty and for the form to process.
Could you please explain what I have to do in order for my form to work properly?
Also, the " require("$_SERVER[DOCUMENT_ROOT]/connect.php"); " part is where my connection to the database code is located. This code and the form code is located in the same page.

Answer 1

Replace require("$_SERVER[DOCUMENT_ROOT]/connect.php"); with require_once $_SERVER[DOCUMENT_ROOT]."/connect.php");, you're not using a variable - the $_SERVER can't be used like you're using it. This is why you're getting a "blank page of death", if you check your error_log you'd see that it has a syntax-error because of it.
Furthermore, you're checking if(!empty($_POST)) - this could really be any POST-form. You should remove this code
if ($_SERVER["REQUEST_METHOD"] == "POST")
{
if(!empty($_POST))
{
as you're checking if the inputs are set just below the above code.
As a final note, when you're using die();, you should use exit; instead. They really do the same thing, but usage of die() is more for error-checking, like "Script can't run any further - die now!", while exit; is more like "I would like to stop the script from running now, I'm done - thanks!".

Answer 2

Normally it’s easier to include the processing code inside the form page. That way, if you encounter errors, you can:
allow the code to fall through to the form again
persist old values by using the value="…" attribute
Roughly it looks like this:
<?php
$email=$username=''; // etc
if(isset($_POST['submit'])) { // or whatever you name the submit button
// validate data
if(!$errors) {
// process
// new location
}
// retain values from above
}
?>
<form>
<label>Name: <input type="text" name="username" value="<?php print $username; ?>"></label>
<label>Email: <input type="text" name="email" value="<?php print $email; ?>"></label>
<!-- etc -->
<button type="submit" name="submit">Send Message</button>
</form>
For ease and management, you can put the PHP code above into a separate file to be included.
The problem your sample above is that although you do redirect to a new page on success, you don’t go anywhere otherwise.
If you want to do it with a separate processing script, you will need to conclude by redirecting back to the original form on failure. However, you will find that persisting old data is more difficult that way.