Remmi

<input type = hidden name = cbx value = 0>
<input type = checkbox name = cbx value = 1>

$_GET['cbx'] = 0;
$_GET['cbx'] = 1;

select v.id, v.fk_id, v.value from `table` as v join (
select fk_id, max(id) as id from `table` where fk_id in (2,4,5) group by fk_id
) targetids using(id)

select t1.*
from tt as t1
inner join (
    select max(id) as max_id
    from tt
    where fk_id in (2,4,5)
    group by fk_id
) as t2 on t1.id = t2.max_id
order by fk_id;

private $lastping=0;
public function ping() {
    if ((time()-$this->lastping)<10) return;
    try {
        self::$dbInstance->query('SELECT 1');
    } catch {
       self::$dbInstance=NULL;
       self::getDB();
    }
    $this->lastping=time();
}