‘Invalid parameter number’ error using bindParam to create an mySQL query

I have written a function that takes four arguments, and passes them to my MySQL database using a PDO.

I am trying to use bindParam so that I can use the variables to construct the query. I have followed the examples in the PHP documentation, but I am getting the following error:

ERROR: SQLSTATE[HY093]: Invalid parameter number: no parameters were bound

What am I doing wrong?

function saveAddress($addressLine1, $addressLine2, $town, $county_id) {

    try {
        $conn = new PDO('mysql:host=localhost;dbname=' . DB_DATABASE, DB_USER, DB_PASSWORD);
        $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        $stmt = $conn->prepare('INSERT INTO address (`address_line_1`, `address_line_2`, `town`, `county_id`)
            VALUES (:addressLine1, :addressLine2, :town, :county_id);');
        $stmt->bindParam(':addressLine1', $addressLine1, PDO::PARAM_STR);
        $stmt->bindParam(':addressLine2', $addressLine2, PDO::PARAM_STR);
        $stmt->bindParam(':town', $town, PDO::PARAM_STR);
        $stmt->bindParam(':county_id', $county_id, PDO::PARAM_INT);     
        $success = $stmt->execute(array());
    }
    catch(PDOException $e) {
        echo 'ERROR: ' . $e->getMessage();
    }
}