The code to populate combo box from database
<td>Item Name:</td>
    <td><select name="items">
        <option value="0" selected="selected"> Choose</option>
        <?php
         while($row = mysql_fetch_assoc($query))
         {
            $category = $row["ItemName"];
            echo "$category";
        ?>
        <option value= <?php $category ?> > <?php echo  $category ?> </option>
        <?php
      }?>
      </select></td>
Code for submit
<td><input type="submit" name="newItem" value="New Item"/></td>
PHP code is:
 <?php
    if(isset($_POST['newItem']))
    {
    $item=$_POST['items'];
    $sel=mysql_query("select ItemID from itemmaster where ItemName='$item'");
    while($row2 = mysql_fetch_array($sel))
    {
               //code
        }
 
    