Mysql::getInstance PHP Method

    public static function getInstance()
    {
        if (!self::$conn instanceof self) {
            self::$conn = new self();
        }
        return self::$conn;
    }

function is_answered($task_id)
{
    $uid = (int) $_SESSION['uid'];
    $sql = "select * from moderators_history where task_id={$task_id} && to_usr!=from_usr order by id desc limit 0,1;";
    $from_usr = Mysql::getInstance()->query($sql)->first('from_usr');
    return $from_usr == $uid;
}