jQuery自动完成PHP Mysql发布不同的字段

I am making use of jQuery's Autocomplete where I am populating my autocomplete dropdown with a php file called site.php. Site.php gets the values from a mysql table called site and which has 3 columns: id, code and site. I want my autocomplete to show only code and site and then store the corresponding id in my other table.

Everything works fine except that autocomplete is posting the code and the site selected but not the id. What do I need to change in order to send the id to my php POST and not code and site? Scripts as follows:

PHP file: site.php

<?php
        $server = 'sql203.com';
        $user = 'xxxxxxxxxxxx';
        $password = 'xxxxxxx';
        $database = 'b17';
    $mysqli = new MySQLi($server,$user,$password,$database);
    /* Connect to database and set charset to UTF-8 */
    if($mysqli->connect_error) {
      echo 'Database connection failed...' . 'Error: ' . $mysqli->connect_errno . ' ' . $mysqli->connect_error;
      exit;
    } else {
      $mysqli->set_charset('utf8');
    }
    /* retrieve the search term that autocomplete sends */
    $term = trim(strip_tags($_GET['term'])); 
    $a_json = array();
    $a_json_row = array();
    if ($data = $mysqli->query("SELECT * FROM `b17_16413362_upupa`.`site` WHERE code LIKE '%$term%' OR site LIKE '%$term%' ORDER BY code , site")) {
        while($row = mysqli_fetch_array($data)) {
            $id = htmlentities(stripslashes($row['id']));
            $code = htmlentities(stripslashes($row['code']));
            $site = htmlentities(stripslashes($row['site']));

            $a_json_row["id"] = $id;
            $a_json_row["value"] = $code.' '.$site;
            $a_json_row["label"] = $code.' '.$site;
            array_push($a_json, $a_json_row);
        }
    }
    // jQuery wants JSON data

    echo json_encode($a_json);
    flush();

    $mysqli->close();
    ?>

Javascript:

<script type="text/javascript">
$(function() {

  $("#sitex").autocomplete({
    source: 'site.php',
     minLength: 0
        }).focus(function(){     

             $(this).autocomplete("search");
  });
});
</script>

In your PHP, change

$a_json_row["value"] = $code.' '.$site;

to

$a_json_row["value"] = $id;

The 'value' property is the data that will be submitted by the form. The 'label' property is what will be displayed to the user.