Message not displaying in <div tag> using Ajax.Updater but opens PHP page instead
===

When the user enters an 'id' of a record and presses the delete button, I am trying to delete that record without the page refreshing and echoing a message in a `<div>` below. 

HTML:

    script language="javascript" type="text/javascript" src="prototype.js"></script>
    <script type="text/javascript">
    function updateDIV(myDiv)
    {
       var url='delete.php';
       var id = $F($('id'));
       var myAjax = new Ajax.Updater(myDiv, url, {method: 'get', parameters: 'id='+id});
    }
    </script>

    </head>

    <body>
        <form action="delete.php" method="get">
            <input type="text" id="id" name="id" placeholder="ID" />
            <input type="submit" value="Delete" onclick="updateDIV(targetDiv)" />
            <div id="targetDiv"></div>
        </form>
    </body>



delete.php:

    <?php require_once('Connections/localhost.php'); ?>
    <?php
    if (!function_exists("GetSQLValueString")) {
    function GetSQLValueString($theValue, $theType, $theDefinedValue = "", $theNotDefinedValue = "") 
    {
      if (PHP_VERSION < 6) {
        $theValue = get_magic_quotes_gpc() ? stripslashes($theValue) : $theValue;
      }
    
      $theValue = function_exists("mysql_real_escape_string") ? mysql_real_escape_string($theValue) : mysql_escape_string($theValue);
    
      switch ($theType) {
        case "text":
          $theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL";
          break;    
        case "long":
        case "int":
          $theValue = ($theValue != "") ? intval($theValue) : "NULL";
          break;
        case "double":
          $theValue = ($theValue != "") ? doubleval($theValue) : "NULL";
          break;
        case "date":
          $theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL";
          break;
        case "defined":
          $theValue = ($theValue != "") ? $theDefinedValue : $theNotDefinedValue;
          break;
      }
      return $theValue;
    }
    }
    
    mysql_select_db($database_localhost, $localhost);
    $query_Recordset3 = "SELECT * FROM orders";
    $Recordset3 = mysql_query($query_Recordset3, $localhost) or die(mysql_error());
    $row_Recordset3 = mysql_fetch_assoc($Recordset3);
    $totalRows_Recordset3 = mysql_num_rows($Recordset3);
    
    mysql_free_result($Recordset3);
    
    if ((isset($_GET['id'])) && ($_GET['id'] != "")) {
      $deleteSQL = sprintf("DELETE FROM orders WHERE id=%s", GetSQLValueString($_GET['id'], "int"));
      
        mysql_select_db($database_localhost, $localhost);
      $Result1 = mysql_query($deleteSQL, $localhost) or die(mysql_error());
      
      if (mysql_affected_rows($localhost) == 1) {
    	echo "The order has been successfully removed";
    	}
    	
    	else {
    		//query failure
    	echo "The order could not be removed due to a system error";
    	}
    
    
    mysql_close($localhost);
    
    }
    
    
    ?>

However when the delete button is clicked I am presented with the delete.php page in the address bar with the corresponding message / blank page with "The order was successfully removed." I would like to know why the message is not being passed to the `<div id="targetDiv"></div>`