I'm trying to create a PHP e-mail activation system for my users, and when I run my script, it returns a blank page and my database was not updated. Any help is appreciated.

Here is my code:

```
<?php

session_start()

$host="localhost"; 
$username="root"; 
$password="power1"; 
$db_name="members"; 
$tbl_name="users";

$link  = mysql_connect($host, $username, $password)or die("cannot connect. Please contact us");
mysql_select_db($db_name)or die("cannot select DB. Please contact us");

$queryString = $_SERVER['QUERY_STRING'];

if(isset($_SESSION[$queryString])) {
  $query = "SELECT * 
              FROM users 
             WHERE email = '$_SESSION[$queryString]'";
  $result = mysql_query($query) or die(mysql_error());
  while($row = mysql_fetch_array($result)) {
    if ($queryString == $row[activationkey]) {
      echo "Congratulations! You have succesfully activated you account. You may now login.";

      $sql = ("UPDATE users 
                 SET activationkey = '' 
                 AND status = 'activated' 
               WHERE username = ".$row['username']);

      if (!mysql_query($sql)) {
        die('Error: ' . mysql_error());
      }
    }
  }
} ?>

```