login form not working
<p>I recently upgraded my version of php and my login form is no longer working.   if i put the correct input.. it does not redirect and instead shows a blank page. I'm still learning and any help would be greatly appreciated.  </p>

<pre><code>&lt;?
session_start();
if(!empty($_SESSION[uname]))
{
    header("location:homepage.php");
    exit();
}
require_once "conn.php";
if(isset($s1))
{
    if(!empty($uname1) &amp;&amp; !empty($upass1))
    {
        $sql = "SELECT * FROM members_info WHERE uname = '$uname1' AND upass = '$upass1'";
        $result = mysql_query($sql);
        if(mysql_num_rows($result) == "1")
        {
            $a = mysql_fetch_array($result);
            $_SESSION[uname] = $uname1;
            header("location:homepage.php");
            exit();
        } 
        else 
        {
            $login_error = "The username and password you entered was invalid.";
        }
    }
}
include_once "main3.php";
?&gt;
</code></pre>
