Hi all

Can someone please tell me what am I doing wrong here, it's a simple dropdown box that populates fine and where I select a member of staff and delete him/her. There are no errors but it will not DELETE why ??????
Many thanks

Code:
include 'connectdb.php';

if(isset($_POST['submit'])){
      $id = mysql_real_escape_string($_POST['id']);
      $sql = "DELETE FROM staff WHERE id = '$id'";
      $result = mysql_query($sql);
      $num = mysql_affected_rows();
      
      if($num == 1){
            echo "<p>Record $id deleted successfully.</p>\n";
      }else{
            echo "<p>Unable to delete record $id.</p>\n";
      }
}
?>
<form method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
<select> 
    <?php $result= mysql_query('SELECT id,forename,surname FROM staff'); 
				while($row= mysql_fetch_assoc($result)) { ?> 
			<?php	echo '<option value="' . $row['id'] . '">' . $row['forename'] . ' '.$row['surname'].'</option>'; 
			} ?>
</select> 

<input type="submit" name="submit" value="Delete" id="delete">
</form>