INSERT query is failing in PHP

I'm sure it's a kickself-obvious typo, but I can't see it. I'm trying to INSERT data taken from a HTML form using POST into a MySQL database using PHP. The POST works successfully, but the query fails; I've checked the table to make sure nothing new has been inserted.

Here's the PHP code intended to run the query:

if ($_POST) {
    $username = "root";
    $password = "root"; //ssh don't tell
    $hostname = "localhost";

    $dbhandle = mysql_connect($hostname, $username, $password) or die("Unable to connect to MySQL");
    $dbname = "asoiaf";
    $tablename = "charlist";

    $id = '3';
    $bookIntroduced = $_POST['bookIntroduced'];
    $pageIntroduced = $_POST['pageIntroduced'];
    $forename = $_POST['forename'];
    $surname = $_POST['surname'];
    $oldSurname = $_POST['oldSurname'];
    $alias = $_POST['alias'];
    $title = $_POST['title'];
    $pageIntroduced = $_POST['regnalNumber'];

    // Below is the query that fails to execute.

    $query = "INSERT INTO $tablename (
            $id, $bookIntroduced, $pageIntroduced, $title, $forename, $surname, $oldSurname, $alias, $regnalNumber
            )";

    mysql_query($query) or die("Nah, I don't feel like being helpful.");

    mysql_close($dbhandle);
}

And here is the structure of the table given by the DESCRIBE command:

Can anyone help me to identify the problem?

Also, if it wasn't clear, I'm new to PHP and SQL.