Php member login Please help

Hi Im trying to make a members login for my site but im having trouble getting any signal that the user has got in success fully. Here is my actionscript and php. My host is netfirms.


login.loginButton.onRelease = function() {
    if (login.userName.length>0 && login.userPassword.length>0) {
        myVars = new LoadVars();
        myVars.username = escape(login.userName.text);
        myVars.pass = escape(login.userPassword.text);
        myVars.action = "login";
        myVars.sendAndLoad("http://www.hiptopdesign.com/login.php", myVars, 'POST');
        myVars.onLoad = function() {
            if (!this.error && this.user>0) {
                //_root.gotoAndStop('registered');
                login.userName.text = "logged in";
                _root.login.lstat.text = myVars;
                trace(myVars);
            } else {
                //_root.gotoAndStop('no_registered');
                login.userName.text = "not logged in";
                _root.login.lstat.text = myVars;
                trace(myVars);
            }
            userName.selectable = true;
            userPassword.selectable = true;
            loginButton.enabled = true;
        };
        //userName.selectable = false;
        //userPassword.selectable = false;
        //loginButton.enabled = false;
    }
};

here is the php


<?php
require_once('db.php');
include('functions.php');
    if(isset($_GET['Login']))
    {
        if($_GET['username']!='' && $_GET['pass']!='')
        {
            //Use the input username and password and check against 'users' table
            $query = mysql_query('SELECT ID, Username, Active FROM users WHERE Username = "'.mysql_real_escape_string($_GET['username']).'" AND Password = "'.mysql_real_escape_string(md5($_GET['pass'])).'"');
            
            if(mysql_num_rows($query) == 1)
            {
                $row = mysql_fetch_assoc($query);
                if($row['Active'] == 1)
                {
                    session_start();
                    $_SESSION['user_id'] = $row['ID'];
                    $_SESSION['logged_in'] = TRUE;
                                        echo $_POST['username'];
                                        print $_POST['username'];
                    header("Location: members.php");
                }
                else {
                    $error = 'Your membership was not activated. Please open the email that we sent and click on the activation link';
                }
            }
            else {        
                $error = 'Login failed !';        
            }
        }
        else {
            $error = 'Please user both your username and password to access your account';
        }
    }
?>

<?php if(isset($error)){ echo $error;}?>
<form action="<?=$_SERVER['PHP_SELF']?>" method="post">
    <input type="text" id="username" name="username" size="32" value="" />
    <input type="password" id="pass" name="pass" size="32" value="" />
    <input type="submit" name="Login" value="Login" />
</form>

please any thoughts would be appreciated