function validateDate($date, $format = 'Y-m-d H:i:s'){
$d = DateTime::createFromFormat($format, $date);
return $d && $d->format($format) == $date;
    }

    if (isset($_POST['register'])) {
if (empty($_POST['date'])) {
    $error = '1';
    $dateError = "Please enter a birthday date.";
} else {
    if ((validateDate($_POST['date'], 'm/d/Y')) == FALSE) {
        $error = '1';
        $dateError = "Please enter a valid birthday date.";
    }
}

if (empty($_POST['username'])) {
    $error = '1';
    $usernameError = "Please enter an username.";
} else
if (strlen($_POST['username']) < 3) {
    $error = '1';
    $usernameError = "Username must have at least 3 characters.";
} else
if (!preg_match("/^[a-z0-9d_]{3,16}$/i", $_POST['username'])) {
    $error = '1';
    $usernameError = "Username can only contain alphabets, underscore characters and numbers.";
} else {
    $sql = "SELECT * FROM users WHERE username=?";
    $stmt = $mysql->prepare($sql);
    $stmt->bind_param('s', $_POST['username']);
    $stmt->execute();
    $result = $stmt->get_result();
    $results = $result->num_rows;
    if ($results >= 1) {
        $error = '1';
        $usernameError = "Username is already in use.";
    }
}

if (!empty($_POST["name"])) {
    if (!preg_match("^(s)*[A-Za-z]+((s)?(('|-|.)?([A-Za-z])+))*(s)*$^", $_POST['name'])) {
        $error = '1';
        $nameError = "Name can only contain alphabets and spaces.";
    }
}

if (!filter_var($_POST['email'], FILTER_VALIDATE_EMAIL)) {
    $error = '1';
    $emailError = "Please enter a valid email address.";
} else {
    $xsql = "SELECT * FROM users WHERE email=?";
    $xstmt = $mysql->prepare($xsql);
    $xstmt->bind_param('s', $_POST['email']);
    $xstmt->execute();
    $xresult = $xstmt->get_result();
    $xresults = $xresult->num_rows;
    if ($xresults >= 1) {
        $error = '1';
        $emailError = "Email is already in use.";
    }
}

if (empty($_POST['password'])) {
    $error = '1';
    $passError = "Please enter a password.";
}
else {
    if (strlen($_POST['password']) < 6) {
        $error = '1';
        $passError = "Password must have at least 6 characters.";
    }
}

if ($error == '0') {
    $name = $_POST['name'];
    $name = substr($name, 0, 40);
    $username = $_POST['username'];
    $username = substr($username, 0, 16);
    $date = $_POST['date'];
    $email = $_POST['email'];
    $password = $_POST['password'];
    $trn_date = date("Y-m-d H:i:s");
    $ip = '';
    if (getenv('HTTP_CLIENT_IP')) {
        $ip = getenv('HTTP_CLIENT_IP');
    }
    else
    if (getenv('HTTP_X_FORWARDED_FOR')) {
        $ip = getenv('HTTP_X_FORWARDED_FOR');
    }
    else
    if (getenv('HTTP_X_FORWARDED')) {
        $ip = getenv('HTTP_X_FORWARDED');
    }
    else
    if (getenv('HTTP_FORWARDED_FOR')) {
        $ip = getenv('HTTP_FORWARDED_FOR');
    }
    else
    if (getenv('HTTP_FORWARDED')) {
        $ip = getenv('HTTP_FORWARDED');
    }
    else
    if (getenv('REMOTE_ADDR')) {
        $ip = getenv('REMOTE_ADDR');
    }
    else {
        $ip = '127.0.0.1';
    }

    $activation = md5($email . time());
    $sql = "INSERT into `users` (username, name, password, email, birthday, status, activation, ip, trn_date, theme, picture, views, currency, publicprofile, showaboutyourself, showviews, changedecimal, sortby, apiscrape, badge, sortfeed, who_can_pm_me, who_can_notify_me, google_auth_code) VALUES (?, ?, ?, ?, ?, ?, '0', ?, ?, ?, 'light', 'default.png', '1', 'USD', '1', '1', '1', '0', 'latestadded', 'coinmarketcap', 'USER', 'relevance', 'all', 'all', ?)";
    $options = ['cost' => 15, ];
    $pdw = password_hash($password, PASSWORD_BCRYPT, $options);
    $stmt = $mysql->prepare($sql);
    $stmt->bind_param('sssssssss', $username, $name, $pdw, $email, $date, $activation, $ip, $trn_date, $secret);
    $stmt->execute();



    // log them in after registration
    $sql = "SELECT id FROM `users` WHERE email=?";
    $stmt = $mysql->prepare($sql);
    $stmt->bind_param('s', $email);
    $stmt->execute();
    $result = $stmt->get_result();
    $row = $result->fetch_assoc();
    $userid = $row["id"];

    $usersession = substr("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ", mt_rand(0, 50) , 1) . substr(md5(time()) , 1) . bin2hex(openssl_random_pseudo_bytes(25));
    $now = time();
    $expires = time() + 86400;
    date_default_timezone_set('Europe/Amsterdam');
    $date = date('d-m-Y');
    $sql = "INSERT INTO sessions (SESSION_ID, SESSION_USER_ID, SESSION_IP, SESSION_EXPIRES, SESSION_DATE, SESSION_ACTIVE, SESSION_AGENT) VALUES (?,?,?,?,?,'1',?)";
    $stmt = $mysql->prepare($sql);
    $stmt->bind_param('ssssss', $usersession, $userid, $ip, $expires, $date, $_SERVER['HTTP_USER_AGENT']);
    $stmt->execute();
    setcookie("MySite_Session_ID", $usersession, $expires, '/');
    header("Location: /");
    die();
}

if (isset($_POST['login'])) {
usleep(500000); // Slow down brute-forcers
$error = '0';
$email = $_POST['email'];
$password = $_POST['password'];
if (empty($email)) {
    $error = '1';
    $userError = "Please enter your email.";
}

if (empty($password)) {
    $error = '1';
    $passError = "Please enter your password.";
}

if ($error == '0') {
    $sql = "SELECT id,password,status FROM `users` WHERE email=?";
    $stmt = $mysql->prepare($sql);
    $stmt->bind_param('s', $email);
    $stmt->execute();
    $result = $stmt->get_result();
    $results = $result->num_rows;
    if ($results >= 1) {
        $row = $result->fetch_assoc();
        if ($row['status'] != 0) {
            if (password_verify($password, $row["password"])) {
                // Password success, log them in

                $userid = $row["id"];
                $useragent = $_SERVER['HTTP_USER_AGENT'];
                $usersession = substr("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ", mt_rand(0, 50) , 1) . substr(md5(time()) , 1) . bin2hex(openssl_random_pseudo_bytes(25));
                $now = time();
                $expires = time() + 86400;
                if (isset($_POST['rememberme'])) {
                    $expires = time() + 15768000;
                }
                date_default_timezone_set('Europe/Amsterdam');
                $date = date('d-m-Y');
                $sql = "INSERT INTO sessions (SESSION_ID, SESSION_USER_ID, SESSION_IP, SESSION_EXPIRES, SESSION_DATE, SESSION_ACTIVE, SESSION_AGENT) VALUES (?,?,?,?,?,'1',?)";
                $stmt = $mysql->prepare($sql);
                $stmt->bind_param('ssssss', $usersession, $userid, $_SERVER['REMOTE_ADDR'], $expires, $date, $_SERVER['HTTP_USER_AGENT']);
                $stmt->execute();
                setcookie("MySite_Session_ID", $usersession, $expires, '/');
                header("Location: /");
            } else {
                $passError = "Invalid password.";
            }
        } else {
            $userError = 'Your account has not been activated. Please check your email.';
        }
    }
}
}

$mysql = mysqli_connect('localhost', 'root', '');
mysqli_select_db($mysql,"mysite");

$sql = "DELETE FROM sessions WHERE SESSION_ID=?";
$stmt = $mysql->prepare($sql);
$stmt->bind_param('s', $_COOKIE['MySite_Session_ID']);
$stmt->execute();

setcookie ('MySite_Session_ID', "", 1);
setcookie ('MySite_Session_ID', false);
unset($_COOKIE['MySite_Session_ID']);

header("Location: /");
exit();

ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
error_reporting(E_ALL);
$mysql = mysqli_connect('localhost', 'root', '');
mysqli_select_db($mysql, "mysite");
date_default_timezone_set('Europe/Amsterdam');

if (isset($_COOKIE['MySite_Session_ID'])) {
$usersession = $_COOKIE['MySite_Session_ID'];
$sql = "SELECT SESSION_USER_ID,SESSION_EXPIRES FROM sessions WHERE SESSION_ID = ? AND SESSION_ACTIVE = '1' AND SESSION_AGENT = ?";
$stmt = $mysql->prepare($sql);
$stmt->bind_param('ss', $usersession, $_SERVER['HTTP_USER_AGENT']);
$stmt->execute();
$dasdasresult = $stmt->get_result();
$results = $dasdasresult->num_rows;
if ($results >= 1) {
    // Is logged in

    $row = $dasdasresult->fetch_assoc();
    $userid = $row["SESSION_USER_ID"];
    $expiretime = $row["SESSION_EXPIRES"];

    if ($expiretime > time()) {
        // Session did not expire

        $sql = "SELECT * from users WHERE id=?";
        $stmt = $mysql->prepare($sql);
        $stmt->bind_param('s', $userid);
        $stmt->execute();
        $dasdasresultx = $stmt->get_result();
        $results = $dasdasresultx->num_rows;
        if ($results >= 1) {
            // User exists

            $row = $dasdasresultx->fetch_assoc();

            $username                       = $row["username"];
            $name                           = $row["name"];
            $userid                         = $row["id"];
            $email                          = $row["email"];
            $loggedin                       = 1;
        } else {
            // User does not exist

            header("Location: /login");
            exit();
        }
    } else {
        // Session expired

        $sql = "UPDATE sessions SET SESSION_ACTIVE = '0' WHERE SESSION_ID = ?";
        $stmt = $mysql->prepare($sql);
        $stmt->bind_param('s', $usersession);
        $stmt->execute();

        header("Location: /login");
        exit();
    }
} else {
    header("Location: /login");
    exit();
}
} else {
    header("Location: /login");
    exit();
}