<?php
$ids = array(1, 2, 3, 7, 8, 9);
$inQuery = implode(',', array_fill(0, count($ids), '?'));
$db = new PDO(...);
$stmt = $db->prepare(
'SELECT *
FROM table
WHERE id IN(' . $inQuery . ')'
);
// bindvalue is 1-indexed, so $k+1
foreach ($ids as $k => $id)
$stmt->bindValue(($k+1), $id);
$stmt->execute();
?>