<?php
//mysql server connection information
$dbhost = "localhost";
$dbname = "web";
$dbuser = "xxx";
$dbpass = "xxx";

//connection query
mysql_connect ( $dbhost, $dbuser, $dbpass)or die("Could not connect: ".mysql_error());
mysql_select_db($dbname) or die(mysql_error());

//gathers information from the .html page and sends it through POST
$code = $_POST['code'];
$username = $_POST['username'];
$password = $_POST['password'];

//if conditions to check if username/password/code field are empty
if(empty($_POST['username'])){
    echo "Username field is empty.";
    exit();
} elseif(empty($_POST['password'])) {
    echo "Password field is empty.";
    exit();
} elseif(empty($_POST['code'])) {
    echo "Code field is empty.";
    exit();
}

//tries to find the code they input in the database
$checkcode = mysql_query("SELECT code FROM codes WHERE code='$code'");
$checkcode_exist = mysql_num_rows($checkcode);

if ($checkcode_exist < 1) {
    echo "No code found.";
    exit();
}

$row = mysql_fetch_row($checkcode); //checks the row of the code they input

if ($row[2] = 1) { //if the third column (ID, CODE, USED) is equal to 1 (the code is used) it will stop running and print error
    echo "Code has already been used!";
    exit();
}

//checks to see if the username they input exists
$checkuser = mysql_query("SELECT username FROM login WHERE username='$username'");
$username_exist = mysql_num_rows($checkuser);

if($username_exist > 0){ //if it exists, print error, unset the $username variable
    echo "Username taken.";
    unset($username);
    include 'index.html';
    exit();
}

$query = "INSERT INTO login (username, password) VALUES('$username', '$password')"; //registery success, insert the username/password they input into the database
$codequery = "UPDATE codes SET used='1' where code='$code'"; //set the value of "used" in the code to 1, preventing them from re-using the same code
mysql_query($query) or die(mysql_error()); //execute above query
mysql_query($codequery) or die(mysql_error()); //execute above query
mysql_close();
print "Registration success!";
exit();
?>