<?php
    require_once('mysql.class.php');

    //  CHANGE THESE TO VALID FOR YOUR
    //  MYSQL CONNECTION DETAILS
    $host = 'localhost';
    $user = 'db_user';
    $pass = 'password';
    $db = 'db_name';
    //  CHANGE THESE TO VALID FOR YOUR
    //  MYSQL CONNECTION DETAILS

    $redirect_unique = 'redir_a.htm';   //  Site to redirect to when the zip-code is not present in the db
    $redirect_exists = 'redir_b.htm';   //  Site to redirect to when the zip-code is present in the db

    if (isset($_POST['zipcode'])) {
        $zip = $_POST['zipcode'];

        $conn_params = array (
            'host' => $host,
            'user' => $user,
            'pass' => $pass,
            'db' => $db
        );
        $conn = new mysql($conn_params);

        $result = $conn->select(array('table' => 'zipcodes', 'condition' => 'zipcode = "'.$zip.'"', 'limit' => 1));
        if (count($result) == 0) {
            // that record was not found do something here
        }
            header('Location: '.$redirect_exists);
            die();
    }
?>