battles/enter.php

<?php
session_start();
include("config.php");
define('ERROR_NO_SUCH_USER', 'Такого пользователя не существует!');
define('ERROR_USER_IS_BLOCKED', 'Пользователь заблокирован!');
define('ERROR_WRONG_PASSWORD', 'Неверный пароль!');
define('ERROR_EMPTY_CREDENTIALS', 'Вы не ввели логин или пароль!');
foreach ($_POST as $key => $val) { //Проверка всех значений массива POST одним махом.
    $_POST[$key] = iconv(mb_detect_encoding($_POST[$key], 'auto'), 'utf-8', $val);
}

$username = filter_input(INPUT_POST, 'username', FILTER_SANITIZE_SPECIAL_CHARS);
$password = $_POST['password'] ?? '';
$battle = $_COOKIE['battle'] ?? '';
$error = "";

if ($username && $password) {
    $user_query = db::c()->query('SELECT `id`, `login` ,`pass`, `room`, `block` FROM `users` WHERE `login` = "?s"', $username)->fetch_assoc();

    if (!$user_query['id']) {
        $error = ERROR_NO_SUCH_USER;
    } elseif ($user_query['block'] == 1) {
        $error = ERROR_USER_IS_BLOCKED;
    } elseif (password_verify($password, $user_query['pass'])) {

        if (!$error) {
            # Проверка на мультоводство по используемому кукису.
            if ($battle != null && $user_query['id'] != $battle) {
                db::c()->query('INSERT INTO users_logs (user_id, type, text) VALUES (?i, "?s", "?s")', $user_query['id'], "multiaccounts", "Разные ID на входе. Возможно используются несколько аккаунтов.");
            }

            setcookie("battle", $user_query['id']);
            $_SESSION['uid'] = $user_query['id'];
            setcookie("uid", $user_query['id'], time() + 43200, "/", GAMEDOMAIN);
            setcookie("hashcode", md5($user_query['id'] . $user_query["pass"] . $user_query["login"]), time() + 43200, "/", GAMEDOMAIN);
            $_SESSION['sid'] = session_id();

            $onl = db::c()->query('SELECT user_id FROM online WHERE user_id = "?s"', $user_query['id'])->fetch_assoc();
            if (isset($onl['user_id'])) {
                db::c()->query('UPDATE online SET date = ?i WHERE user_id = "?s"', time(), $user_query['id']);
            } else {
                db::c()->query('INSERT INTO online (user_id, date, room, real_time) VALUES (?i, ?i, ?i, ?i)', $user_query['id'], time(), $user_query['room'], time());
            }

            db::c()->query('UPDATE `users` SET `session_id` = "?s", `enter_game` = ?i WHERE `id` = ?i', session_id(), 1, $user_query['id']);
            header("Location: fight.php");
        }
    } else {
        $error = ERROR_WRONG_PASSWORD;
    }
} else {
    $error = ERROR_EMPTY_CREDENTIALS;
}

Template::header('Входим...');

if ($error) {
    echo sprintf('<a href="/"> ← на главную</a><h1>%s</h1>', $error);
}