Untitled

<?php include_once("scripts/global.php");
$message = '';
if(isset($_POST['username']) && !empty($_POST['username'])){

    $username = $_POST['username'];
    $fname = $_POST['fname'];
    $lname = $_POST['lname'];
    $email = $_POST['email'];
    $pass1 = $_POST['pass1'];
    $pass2 = $_POST['pass2'];

    //error handling
    if ((!$username)||(!$fname)||(!$lname)||(!$email)||(!$pass1)||(!$pass2)) {
        $message = "Please insert all fields in the form below";
    } else {
        if($pass1 != $pass2){
            $message= "Your password fields do not match";
        }else{
            //securing the data
            $username = preg_replace("#[^0-9a-z]#i","",$username);
            $fname = preg_replace("#[^0-9a-z]#i","",$fname);
            $lname = preg_replace("#[^0-9a-z]#i","",$lname);
            $pass1 = sha1($pass1);
            $email=mysql_real_escape_string($email);

            //check for duplicates
            $user_query=mysql_query("SELECT username FROM members WHERE username='$username'LIMIT 1") or die ("Could not check username");
            $count_username = mysql_num_rows($user_query);
            $email_query=mysql_query("SELECT email FROM members WHERE email='$email'LIMIT 1") or die ("Could not check email");
            $count_email = mysql_num_rows($email_query);
            if($count_username > 0){
                $message ='Your username is already in use';
            }else if($count_email >0){
                $message='Your email is already in use';
            }else{
                $ip_address = $_SERVER['REMOTE_ADDR'];
                $query = mysql_query("INSERT INTO members (username, firstname, lastname, email, password, ip_address, sign_up_date) VALUES ('$username', '$fname', '$lname', '$email', '$pass1', $ip_address', now())")or die("Could not insert your information");
                $member_id = mysql_insert_id();
                mkdir("users/$member_id",0755);
                $message= "Register complete";
            }
        }
    }
}
?>
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Untitled</title>
<link href="css/global.css" rel="stylesheet" type="text/css"/>
</head>
<body>
<div class="container center">
    <h1>Register</h1><br>
    <p><?php print("$message");?></p>
    <form action="register.php" method="post">
            <input type="text" name="username" placeholder="Username" /><br />
            <br /><input type="text" name="fname" placeholder="First name" /><br />
            <br /><input type="text" name="lname" placeholder="Last name" /><br />
            <br /><input type="text" name="email" placeholder="Email Address" /><br />
            <br /><input type="password" name="pass1" placeholder="Password" /><br />
            <br /><input type="password" name="pass2" placeholder="Validate Password" /><br />
            <br /><input type="submit" value="Submit" />
    </form>
    </div>
</body>
</html>