Need help : HTTP

<?php
	// make sure we can redirect (this was just a nice little function that made redirects nicer to user over and over)
	// for your case you would most likely use die("why it died") so that the browser gets the error, and computercraft gets the error message
	// so that you can tell your user why the registration failed
	// NOTE: the scripts at the other end are designed to receive a GET, which is why the redirects are formatted in the way they are (plus its easier to do GET than POST from PHP)
	require_once($_SERVER['DOCUMENT_ROOT'] . "eta/functions/redirect.php");

	if (!isset($_POST['rpass'])){ redirect('index.php?e'); }

	// The salt is just a bunch of random data to help further hide the hashed password and make it harder to do a lookup on the hashed password
	// each user has a different salt so that even two passwords if the same, have different hashed values
	$salt = hash("sha256",mcrypt_create_iv(64));

	// get the register details from the post data
	$input_username = urldecode($_POST["user"]);
	$input_email = urldecode($_POST["email"]);
	$input_password = urldecode($_POST["pass"]);
	$input_repeat_password = urldecode($_POST["rpass"]);

	// deleted variable validation... not needed for this example to you Thib0704

	// create a new mysql connection
	$connection = new mysqli($db_host, $db_user, $db_pass, $db_name);

	// make sure there is a connection
	if (mysqli_connect_error()) { redirect('register.php?d'); }

	// create a prepared statement to check if the username exists already, the ? is where values will end up going
	$query = "SELECT COUNT(username) FROM user WHERE username = ?;";

	// create the statement
	$stmt = $connection->prepare($query);

	// fill in the blanks that were in the query, i.e. place the username in the ? ... s means string, there are other letters for other data types
	$stmt->bind_param("s", $input_username);

	// check if the execution succeeded
	if (!$stmt->execute()){ redirect('register.php?d'); }

	// bind the returned data to variables, this gets the return result from the database and adds it into the $usersWithThatName variable
	$stmt->bind_result($usersWithThatName);

	// complete the process
	$stmt->fetch();

	// make sure no other users have the same username
	if($usersWithThatName != 0){ redirect('register.php?x'); }

	// close the mysql statement, don't close the connection, we have more to do still
	$stmt->close();

	// create a prepared statement to make sure the email hasn't been used before, the process is exactly the same as above
	$query = "SELECT COUNT(email) FROM user WHERE email = ?;";
	$stmt = $connection->prepare($query);
	$stmt->bind_param("s", $input_email);
	if (!$stmt->execute()){ redirect('register.php?d'); }
	$stmt->bind_result($usersWithThatEmail);
	$stmt->fetch();
	if($usersWithThatEmail != 0){ redirect('register.php?l'); }
	$stmt->close();

	// append the salt to the input password and then hash it, making sure to use the same hashing algorithm otherwise the weakest link is the lower hash algo
	$hashed_password = hash("sha256", $input_password . $salt);

	// create a prepared statement to insert many variables into the table (we have to insert the salt so we can know what the users salt is later)
	$insert_stmt = "INSERT INTO user (username, password, salt, email, securityLevel) VALUES(?, ?, ?, ?, 1);";
	$stmt = $connection->prepare($insert_stmt);

	// now notice that we have an 's' per ?, so for each ? you must have a value to put into it, again this is a bad example because all we used were varchar2 everywhere
	// as that was all we needed to use, but there are other letters for other data types
	$stmt->bind_param("ssss", $input_username, $hashed_password, $salt, $input_email);

	if (!$stmt->execute()){ redirect('register.php?d'); }

	// I left this in just so you could see that you can get the primary key of the result, in this case for us it was a number as the unique user id and we then made
	// a folder for them on the server
	$userId = $connection->insert_id;
	mkdir($_SERVER['DOCUMENT_ROOT'] . 'eta/user_data/' . $userId);

	// this line takes us back to a page, but below the closing php tag you could just have html code like "registration successful" and that is:
	// 1 what the browser will show and
	// 2 the only text computercraft will get back
	redirect('index.php?s');
?>