从html表单数组更新mysql表

Question

I'm using a cms and i'm trying to create a snippet that updates a mysql table from an html form array.

This is my form which creates a few input tags and works fine:

while ($data1 = mysql_fetch_array($result1)) {
    $productgroup_id = $data1["productgroup_id"];
    $productgroup_name = $data1["productgroup_name"];
    $list = $data1["list"];

        echo '
            <tr>
                <td class="fieldlabel" width="30%">'.$productgroup_name.' Group</td>
                <td class="fieldarea"><input type="text" name="list[]" size="30" value="'.$list.'"> List ID</td>
            </tr>
            ';
}

This is my code to update the database which does not work:

  if(isset($_POST['submit'])) {
        $list = $_POST['list'];
        foreach($list as $value){
            $update = array(
                $list[] = $value,
            );
        update_query("mod_lists", $update, "");
    }