Untitled

<!doctype html>
<html>
<head>
<title>Register</title>
    <link href='http://fonts.googleapis.com/css?family=questrial' rel='stylesheet' type='text/css'>
</head>
<body>
<p><a href="register.php">Register</a> | <a href="login.php">Login</a></p>
<h3>Registration Form</h3>
<form action="" method="POST">
Username: <th><input type="text" name="username"></th>
Password: <th><input type="password" name="password"></th>
<input type="submit" value="Register" name="submit">
</form>
<?php

    if($_POST['submit']) {
        $username=$_POST['username'];
        $password=$_POST['password'];
    }

    $con=mysql_connect('localhost', 'root', '') or die(mysql_error());
    mysql_select_db('details') or die ("Cannot select Database");
    //If someone tries to Enter John then JOHN then JoHn. Only one will be used and it won't make duplicate usernames
    $query=mysql_query("SELECT * FROM user WHERE username='".$username."'");
    $numrows=mysql_num_rows($query);

    if($numrows!=0){
        echo"Username exists";
    } else {
        mysql_query("INSERT INTO user(username,password) values('$username', '$password')");
        header("location:login.php");
    }

    ?>
</body>
</html>