Help with secure login/registration

I Posted in another forum but I'm not getting any suggestions. Hopefully you all can help me.

I have looked everywhere the past 2 days.  I have flip-flopped this thing a million different ways - still no luck.
Can someone PLEASE help me and tell me what I need to do to get this thing working?
I found this script online for secure login, there was no registration page included so I have been trying to make one work.
As of now it goes from the registration page(form) to process_registration (this page) then should redirect to index.htm if it is successful.  If there is no password entered, it should just say error.

I get connected to the database , "Localhost via UNIX socket" is what I get in the browser.  No entries, however.

Thanks a lot

<script type="text/javascript" src="sha512.js"></script>
<?php

include 'db_connect.php';


if (isset($_POST['password'])) {
$Username = $_POST['username'];
$Email = $_POST['email'];
$Password1 = $_POST['password'];
$Random_Salt = hash('sha512', uniqid(mt_rand(1, mt_getrandmax()), true));
$Password = hash('sha512', $Password1.$Random_Salt);
$ip = $_SERVER['REMOTE_ADDR'];
$ml = $_POST['mailinglist'];


$insert_stmt = $mysqli->prepare('INSERT INTO members (username, email, password, salt, ipaddress, date, mailinglist) VALUES (?, ?, ?, ?, ?, ?, ?)');
$insert_stmt->bind_param('sssssis', $Username, $Email, $Password, $Random_Salt, $ip, NOW(), $ml);
$insert_stmt->execute();
header ['Location: index.htm'];
}
	else
	{
		echo 'ERROR';
	}


?>