<?php
    $output = NULL;
    $ip = $_SERVER['REMOTE_ADDR'];
    if (isset($POST['submit'])) {
        $username = $mysqli->real_escape_string($_post['username']);
        $password = $mysqli->real_escape_string($_post['password']);
        $rpassword = $mysqli->real_escape_string($_post['rpassword']);
        $email = $mysqli->real_escape_string($_post['email']);
        $query = $mysqli->query("SELECT * FROM users WHERE username = '$username'");
        if (empty($username) OR empty($password) OR empty($email) or empty($rpassword)) {
            $output = "Please fill in all fields!";
        } elseif ($query->num_rows != 0) {
            $output = "That username is already taken!";
        } elseif ($rpassword != $password) {
            $output = "Password does not match!";
        }
    }
?>
Later on in the script, I use this:
<?php
echo $output;
?>
It does not echo, and yes, I have added the mysqli query, but I removed it for the safety of the database. You can also see that it does not echo at the website: vobern.com
 
     
     
     
    