<select>
<?php
$urunsor = $DB->query("SELECT  * FROM urunler");
$urunsor->execute();
while($uruncek = $urunsor->fetch(PDO::FETCH_ASSOC)) {
?>
<option value="<?=$uruncek['urun_id]?>"><?=$uruncek['urun_ad]?></option>
<?php } ?>
</select>