$email = isset($_POST['email']) ? $_POST['email'] : false;
$name = isset($_POST['name']) ? $_POST['name'] : false;
$phone_number = isset($_POST['phone_number']) ? $_POST['phone_number'] : false;
$age = isset($_POST['age']) ? $_POST['age'] : false;
$gender = isset($_POST['gender']) ? $_POST['gender'] : false;
$annual_income = isset($_POST['annual_income']) ? $_POST['annual_income'] : false;
// Check for Data
if ($username === false || $password === false || $email === false || $name === false || $phone_number === false || $age === false || $gender === false || $annual_income === false) {
    SendSingleError(HTTP_BAD_REQUEST, "one or more fields not found", ERRTXT_UNSETVARIABLE);
} else {
    // Make sure we don't already have someone with that username
    $query = "SELECT username FROM registered_users WHERE username = '******' ";
    $data = $databaseConnection->query($query);
    if ($data->num_rows > 0) {
        SendSingleError(HTTP_BAD_REQUEST, "someone else already has this username", "Sorry, but someone else has already claimed this username.  Please try again with a new username. ");
    } else {
        // Write data to database
        $query = "INSERT INTO registered_users (username, name, password, email, phone_number, age, annual_income, gender) VALUES('{$username}', '{$name}', '{$password}', '{$email}', '{$phone_number}', '{$age}', '{$annual_income}', '{$gender}')";
        if ($databaseConnection->query($query)) {
            // If query was successful
            header(HTTP_OK);
            header(API_RESPONSE_CONTENT);
            echo json_encode(TRUE);
            exit;
        } else {
            SendSingleError(HTTP_INTERNAL_ERROR, 'failed to insert new user into database', ERRTXT_FAILED_QUERY);
        }
    }
}
SendSingleError(HTTP_INTERNAL_ERROR, 'php failed', ERRTXT_FAILED);
function TopLevelExceptionHandler($exception)
{
    SendSingleError(HTTP_INTERNAL_ERROR, $exception->getMessage(), 'Uh oh! Something went terribly wrong. 😢');
}