Scratch

<link rel="stylesheet" type="text/css" href="global.css" />
<?php
if(isset($_POST['submit'])) {

include "demo.html";

//Database Information
 
$dbhost = '*';
$dbuser = '*'; 
$dbpass = '*';
$dbname = '*';
 
//Connect to database
 
mysql_connect ( $dbhost, $dbuser, $dbpass)or die("Could not connect: ".mysql_error());
mysql_select_db($dbname) or die(mysql_error());

$email = $_POST['email'];    
$username = $_POST['username'];
$password = ($_POST['password']);
 
// lets check to see if the username already exists
 
$link = mysql_connect("*", "*", "*");
mysql_select_db("*", $link);
 
$checkuser = mysql_query("SELECT username FROM login WHERE username='$username'", $link);

$num_rows = mysql_num_rows($checkuser); //this is line 30
 
if($username_exist > 0){
    echo "<p>The username $username is already taken. Please retry.</p>";
    unset($username);
    include 'registration.html';
    exit();
}
 
// lf no errors present with the username
// use a query to insert the data into the database.

$ip = $_SERVER['REMOTE_ADDR'];

$query = "INSERT INTO login (user, pass, ban, email, ip)
VALUES('$username', '$password', 'false', '$email', '$ip')";
mysql_query($query) or die(mysql_error());
mysql_close();
 
echo "<p>You are now registered! Your account details have been sent to $email!</p>";
   
// mail user their information
 
$yoursite = 'Mini Universe Service';
$webmaster = 'Mini Universe Website Service';
$youremail = '*';
   
$subject = "Mini Universe - Account Details";
$message = "Thank you for registering at Mini Universe! You can login now with the following details:

Username: $username
Password: $password

We hope you have fun sharing, and downloading planets!";
   
mail($email, $subject, $message, "From: $yoursite <$youremail>\nX-Mailer:PHP/" . phpversion());
   
echo "<p>You are ready to log in! We have sent your info to your email.</p>";
 } else {
 header('Location: http://www.plaxon.comyr.com/error404.php');
 }
?>