无法更改数据库

My aim to is to Update Value in Database By using Update Query . On my first page i have just displayed database table in webpage. Then by using hyperlink i have to click on Edit to second page "edit.php".While on first page i have to get the value of id and send it to second page. Where a input form is displayed which gets Value casually but Id through hidden tag. On third page getting the values query is implented but the value of id is missing.

First Page

<html>
<head>
 <title>Assignment</title>
 </head>

<body>
 <?php
     $con=mysql_connect("localhost","root","");
     // Check connection
    if (!mysql_connect()) {
        echo "Failed to connect to MySQL: " . mysql_connect_error();
    }
     $db=mysql_select_db("assignment",$con);

     $result = mysql_query("SELECT * FROM teacher ",$con);
    ?><table cellpadding="2px" border="2px"><?php
    while($row = mysql_fetch_array($result)) {
     ?> <tr>
          <td><a href="edit.php?id=<?php       
        echo $row['id'];  ?>">Edit</a > <a href="delete.php">Delete</a>
                 </td><td>
             <?php       
        echo $row['id'];  ?></td><td> <?php echo $row['name'];?></td><td><?php echo $row['program']; ?></td>
               <?php   }
          ?></table><?php
    mysql_close($con);
 ?>

</body>
</html>  

Secnod Page edit.php

<html>
<head>
      <title>Assignment Edit</title>
    </head>
<body>
 <?php
    $id = $_GET['id'];
 ?>
    <form action="update.php" method="get">
       Address <input type="text" name="program"><br>
       <input type="hidden" name="id" value='<?php $id?>'>
        <input type="submit" name="submit">
    </form>

</body> 
</html>

Third Page update.php

<html>
<head>
      <title>Update Page</title>
      </head>

      <body>

  <?php
       $add=$_GET['program'];
       $id=$_GET['id'];
       $con=mysql_connect("localhost","root","");
     // Check connection
       if (!mysql_connect()) {
          echo "Failed to connect to MySQL: " . mysql_connect_error();
        }
       $db=mysql_select_db("assignment",$con);
        $query = "UPDATE teacher SET program='$add' WHERE id =".$id;
        echo $query;
       $result = mysql_query($query,$con);

      /* while($row = mysql_fetch_array($result)) {
          echo $row['id'] ." " .  $row['name']." ".  $row['address']."<br>"; 
               }
       mysql_close($con);
  */
  ?>
  </body>
</html>

output

UPDATE teacher SET program='openSource' WHERE id =

you need to change this

   <input type="hidden" name="id" value='<?php $id?>'>

to

   <input type="hidden" name="id" value='<?php echo $id?>'>

(or)

   <input type="hidden" name="id" value='<?=$id?>'>