PHP PDO->bindValue() vs row execute speed difference

Hi,
I have following situation:
$q = 'select * from tbl1 where id = :id';
$stmt = $dbh->prepare($q);
$stmt->bindValue(':id', $id , PDO::PARAM_INT);
$stmt->execute();
//1000 ms
and

$q1 = ' select * from tbl1 where id = 100 ';
$stmt = $dbh->prepare($q);
//NO binding here !
$stmt->execute();
//2 ms

The queries are a bit more complex, but this is enough to get the idea.

So the first query runs for about 1000 ms

The second query( w/o binding) runs for about 2 ms.
If I'm correct, the first query is interpreted as : select * from tbl1 where id = (INT )
and I don't get good execution plan.

The second one is fast, because  the DB see the literal 100 as value for ID and makes a better execution plan.
Am I correct in my thoughts ?
Is there anything I can do in tuning the DB or just to skip/rewrite PHP PDO ?