Column 'custID' cannot be null - php

Question

I'm trying to use this php document to use a form to input information into a database. I keep getting the same error, Column 'custID' cannot be null. I don't know whats wrong or what to do. I might have to take the L for this assignment but it would be helpful if I could get an answer in case I run into the same problem in the future.
I already tried doing NOT NULL AUTO_INCREMENT in the mysql code. i also tried doing the same thing by using NULL for custID. Neither worked.
if(isset($_POST['submit'])){
$data_missing = array();
if(empty($_POST['custID'])){
$data_missing[] = 'Customer ID';
}else{
$custID = trim($_POST['custID']);
}
if(empty($_POST['custFirstName'])){
$data_missing[] = 'First Name';
}else{
$custFirstName = trim($_POST['custFirstName']);
}
if(empty($_POST['custLastName'])){
$data_missing[] = 'Last Name';
}else{
$custLastName = trim($_POST['custLastName']);
}
if(empty($_POST['address'])){
$data_missing[] = 'Address';
}else{
$address = trim($_POST['address']);
}
if(empty($_POST['city'])){
$data_missing[] = 'city';
}else{
$city = trim($_POST['city']);
}
if(empty($_POST['custstate'])){
$data_missing[] = 'State';
}else{
$custstate = trim($_POST['custstate']);
}
if(empty($_POST['custEmail'])){
$data_missing[] = 'Email';
}else{
$custEmail = trim($_POST['custEmail']);
}
if(empty($_POST['custPhone'])){
$data_missing[] = 'Phone';
}else{
$custPhone = trim($_POST['custPhone']);
}
if(empty($_POST['Password'])){
$data_missing[] = 'Password';
}else{
$Password = trim($_POST['Password']);
}
}
if(empty($data_missing)){
require_once '../LabYourLastProject/mysqli_connect.php';
$query = "INSERT INTO Customers (custID, custFirstName, custLastName, address, city,"
. " custstate, custEmail, custPhone, Password) VALUES ( ?, ?, ?, ?, ?, ?, ?, ?, ?)";
$stmt = mysqli_prepare($dbc, $query);
mysqli_stmt_bind_param($stmt, "sssssssss", $custID, $custFirstName,$custLastName, $address, $city, $custstate, $custEmail, $custPhone, $Password);
mysqli_stmt_execute($stmt);
$affected_rows = mysqli_stmt_affected_rows($stmt);
if($affected_rows == 1){
echo 'Student Entered';
mysqli_stmt_close($stmt);
mysqli_close($dbc);
}else{
echo 'Error Occurred <br />';
echo mysqli_error($dbc);
}
}else{
echo'You need to enter the following data<br />';
foreach($data_missing as $missing){
echo "$missing<br />";
}
}
Its supposed to insert the data passed from the form in another file into a database and show what data is missing. I just get the error.

Answer 1

You have to remove custID because is an AUTO_INCREMENT
$query = "INSERT INTO Customers (custFirstName, custLastName, address, city,"
. " custstate, custEmail, custPhone, Password) VALUES (?, ?, ?, ?, ?, ?, ?, ?)";
and this code
mysqli_stmt_bind_param($stmt, "sssssssss", $custFirstName,$custLastName, $address, $city, $custstate, $custEmail, $custPhone, $Password);

Answer 2

When inserting data to a database table the primary key which for your case is custID needs to be left out as it is not necessary here. It will be taken care by the server. Good thing you have put it to be auto_increment. You can include it in your insert code only when you have a value that is unique. But under normal circumstance leave it blank and insert other fields
$query = "INSERT INTO Customers (custFirstName, custLastName, address, city,"
. " custstate, custEmail, custPhone, Password) VALUES (?, ?, ?, ?, ?, ?, ?, ?)";