mysql_query("UPDATE `users` SET `balans` = '" . $user['balans'] . "' WHERE `id` ='" . $user['id'] . "' LIMIT 1");
На
mysql_query("UPDATE `users` SET `balans`=balans+'". $user['balans'] . "' WHERE `id` ='" . $user['id'] . "' LIMIT 1");
mysql_query("UPDATE `users` SET `balans` = '" . $user['balans'] . "' WHERE `id` ='" . $user['id'] . "' LIMIT 1");
mysql_query("UPDATE `users` SET `balans`=balans+'". $user['balans'] . "' WHERE `id` ='" . $user['id'] . "' LIMIT 1");