$query = $conn->prepare('SELECT * FROM '.$tb['feed'].' WHERE '.$feed['user'].' IN
                        (SELECT * FROM '.$tb['conre'].' WHERE '.$cr['to'].' = :u_id OR '.$cr['from'].' = :u_id AND '.$cr['state'].' = :state)
                        OR '.$feed['about'].' IN
                        (SELECT * FROM '.$tb['conre'].' WHERE '.$cr['to'].' = :u_id OR '.$cr['from'].' = :u_id AND '.$cr['state'].' = :state)
                        OR '.$feed['user'].' = :u_id OR '.$feed['about'].' = :u_id
                        ORDER BY datetime DESC LIMIT 20');
$query->execute(array(
    ':u_id' => $user_id,
    ':state' => $state
));
$result = $query->fetchAll();