<?php
    require_once('dbconnect.php');

    $username = mysql_real_escape_string($_POST['username']);
    $password = md5(mysql_real_escape_string($_POST['password']));
    $error = NULL;

    if((!isset($username)) || (!isset($password))){
        echo "Please fill in all fields";
        echo "<br><a href='../register.php'>Go Back</a>";
        $error = 1;
        exit();
    }
    if(!filter_input(INPUT_POST, 'email', FILTER_VALIDATE_EMAIL)) {
        echo "Please enter a valid email address";
        echo "<br><a href='../register.php'>Go Back</a>";
    } else
        $email = $_POST['email'];

    $sql = mysql_query("SELECT * FROM `users` WHERE username='$username'");
    $sql2 = mysql_query("SELECT * FROM `users` WHERE email = '$email'");

    if(mysql_num_rows($sql2) != 0){
        echo "Email address is already registered";
        echo "<br><a href='../register.php'>Go Back</a>";
        $error = 1;
        exit();
    }

    if(mysql_num_rows($sql) != 0){
        echo "Username already exists";
        echo "<br><a href='../register.php'>Go Back</a>";
        $error = 1;
        exit();
    }

    if($error == 1){
        exit();
    }

    $sql3 = mysql_query("INSERT INTO `users` VALUES ('','$username','$password','$email')");
    if($sql3){
        echo "Thank you, you have been registered";
        echo "<br><a href='../index.php'>Login</a>";
    } else {
        echo "There was an error";
        echo "<br><a href='../register.php'>Go Back</a>";
    }
?>