<?php
        $conn = mysql_connect("localhost", "....", "....") or die(mysql_error());
        $username = mysql_real_escape_string($_POST['username']);
        if(strlen($username)>=20 or strlen($username)<=3) {$usershort = exit ("Username too short.");}
        $password = md5($_POST['password']);
        //if(strlen($password)>=20 or strlen($password)<=3) {$passshort = exit ("Password too short.");}//
        $email = mysql_real_escape_string($_POST['email']);
        if(strlen($email)>=25 or strlen($email)<=5) {$emailshort = exit ("Forgot to type in your email?"); }

        $numrows = mysql_num_rows(
            mysql_query("SELECT * FROM Users WHERE username='$username'")
        );
        if($numrows >= 1) {exit("Username exists."); }

        $sql="INSERT INTO Users (UserName, Password, Email)
        VALUES
        ('$username','$password', '$email')";

        if (!mysql_query($sql,$conn))
        {
        die('Error: ' . mysql_error());
        }
        echo "You have successfully registered";

        mysql_close($conn);
?>