<?php
## Displaying form is no form has already been submitted
if(!isset($_POST['submit'])) {

## Creating a 'goto' point for later use
form: {
?>
<form action='<?php echo $_SERVER['PHP_SELF']; ?>' method='post'>
Username: <input type='text' name='username' /><br />
Password: <input type='text' name='password' /><br />
Password Confirmation: <input type='text' name='passwordc' /><br />
Email: <input type='text' name='email' /><br />
<input type='submit' name='submit' value='Sign Up' />
</form>
<?php
}
}

## Processing if a form has been submitted
else {

## A little security measure
$username = mysql_real_escape_string($_POST['username']);
$username = htmlentities($username);
$password = mysql_real_escape_string($_POST['password']);
$passwordc = mysql_real_escape_string($_POST['passwordc']);
$email = mysql_real_escape_string($_POST['email']);

## Connecting to the database, you need to fill in with your information
$con = mysql_connect('localhost', 'username', 'password');
mysql_select_db('dbname', $con);

## Checking to see if the username has been taken
$check = sprintf("SELECT * FROM users WHERE Username='%s'", $username);
$check_ = mysql_query($check);
$check__count = mysql_num_rows($check_);

if($check__count > 0) { echo 'We already have a user signed up with that username. <br /><br />'; goto form; }

## Checking to see if passwords match
if($password != $passwordc) { echo 'Your two passwords do not match. <br /><br />'; goto form; }

## Checking length of password
if(strlen($password) < 4) { echo 'Your password is too short. Must be more than 4 characters. <br /><br />'; goto form; }

## Checking to see if the email is taken
$check = sprintf("SELECT * FROM users WHERE Email='%s'", $email);
$check_ = mysql_query($check);
$check__count = mysql_num_rows($check_);

if($check__count > 0) { echo 'We already have a user signed up with that email. <br /><br />'; goto form; }

## Inserting information to the database, with the 'Type' set to 0, which means the account is not activated. You'll need to change it to 1 in order to activate the account
$query = "INSERT INTO users (Username, Password, Email, Type) VALUES ('$username', '$password', '$email', '0')";
mysql_query($query);

## Sending a mail to you
$to = 'youremail@yourdomain.com';
$subject = 'User in need of activation';
$message = 'A user has just registered with the username: ' . $username . '. He is need of activation.';

mail($to, $subject, $message);
}
?>