I have created a client address book, but can't seem to add new clients

Question

I have created an address book for my clients app. I can log in and out. The data is not remembered by the browser when I hit refresh, redirect to log back in, all that is good, but after adding the file below to add new clients. I am unable to do so. Could someone assist me in identifying why I cannot successfully add new clients?

<?php
session_start();

// if user is not logged in
if(!$_SESSION['loggedInUser']) {

    // send them to the login page
    header("Location: index.php");
}

// connect to the database
include('includes/connection.php');

// include functions file
include('includes/functions.php');

// if add button was submitted
if(isset($_POST['add'])) {

    // set all variables to empty by default
    $clientName = $clientEmail = $clientPhone = $clientAddress =$clientCompany = $clientNotes = "";

    // check to see if inputs are empty
    // create variables with form data
    // wrap the data with our function

    if($_POST["clientName"]) {
        $nameError = "Please enter a name <br>";
    } else {
        $clientName = validateFormData($_POST["clientName"]);
    }

    if($_POST["clientEmail"]) {
        $emailError = "Please enter a email <br>";
    } else {
        $clientEmail = validateFormData($_POST["clientEmail"]);
    }

    // these inputs are not required
    // so we'll just store whatever has been entered
    $clientPhone    = validateFormData($_POST["clientPhone"]);
    $clientAddress    = validateFormData($_POST["clientAddress"]);
    $clientCompany    = validateFormData($_POST["clientCompany"]);
    $clientNotes    = validateFormData($_POST["clientNotes"]);

    // if required fields have data
    if($clientName && $clientEmail) {

        // create query
        $query = "INSERT INTO client(id, name, email, phone, address, company, notes, date_added) VALUES(NULL, '$clientName', '$clientEmail', '$clientPhone', '$clientAddress', 'clientCompany', 'clientNotes', CURRENT_TIMESTAMP)";

        $result = mysqli_query($conn, $query);

        // if query was successful
        if($result) {

            // refresh page with query string
            header("Location: clients.php?alert=success");
        } else {

            // something went wrong
            echo "Error: ".$query."<br>".mysqli_error($conn);
        }
    }
}

// close the mysql connection
mysqli_close($conn);



include('includes/header.php');
?>

<h1>Add Client</h1>

<form action="<?php echo htmlspecialchars($_SERVER['PHP_SELF']); ?>" method="post" class="row">
    <div class="form-group col-sm-6">
        <label for="client-name">Name *</label>
        <input type="text" class="form-control input-lg" id="client-name" name="clientName" value="">
    </div>
    <div class="form-group col-sm-6">
        <label for="client-name">Email *</label>
        <input type="text" class="form-control input-lg" id="client-email" name="clientEmail" value="">
    </div>
    <div class="form-group col-sm-6">
        <label for="client-phone">Phone</label>
        <input type="text"
 class="form-control input-lg" id="client-phone" name="clientPhone" value="">
    </div>
    <div class="form-group col-sm-6">
        <label for="client-address">Address</label>
        <input type="text" class="form-control input-lg" id="client-address" name="clientAddress" value="">
    </div>
    <div class="form-group col-sm-6">
        <label for="client-company">Company</label>
        <input type="text" class="form-control input-lg" id="client-company" name="clientCompany" value="">
    </div>
    <div class="form-group col-sm-6">
        <label for="client-notes">Notes</label>
        <textarea type="text" class="form-control input-lg" id="client-notes" name="clientNotes"></textarea>
    </div>
    <div class="col-sm-12">
        <a href="clients.php" type="button" class="btn btn-lg btn-default">Cancel</a>
        <button type="submit" class="btn btn-lg btn-success pull-right" name="add">Add Client</button>
    </div>
</form>

<?php
include('includes/footer.php');
?>

Answer 1

Check that your "client" table allows ID value as NULL. I believe that's the problem because if you setup your table correctly that would be your primary key which should not be NULL.